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Nursing Math & Dosage Foundations · 500-Question Practice Bank (worked answers)

Basic IV Infusion Rates (Part 2) — practice set

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40 dosage-calculation problems with a full worked answer for each: dimensional-analysis setup, raw calculation, rounding rule, final labeled answer, rationale and clinical pearl. Work each one on paper first, then open the answer.

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40 review questions from the chapter. Try each one, then open the answer.

  1. Question 261. Scenario: A 62-year-old adult returns from abdominal surgery and is placed on maintenance IV fluids. Order: Infuse 1,000 mL 0.9% sodium chloride (normal saline) IV over 8 hours. Available: 1,000 mL bag of 0.9% sodium chloride; electronic infusion pump. Question: At what rate (mL/hr) should the infusion pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 125 mL/hr Setup (dimensional analysis): Rate (mL/hr) = total volume ÷ time = 1,000 mL ÷ 8 hr Raw calculation: 1,000 ÷ 8 = 125 Rounding: 125 is already a whole number; no rounding needed. Final answer: 125 mL/hr Rationale: To find a pump rate, divide the total volume to be infused by the total infusion time in hours. 1,000 mL delivered evenly over 8 hours requires 125 mL every hour. Clinical pearl: mL/hr is the same as "volume per hour"; always confirm the time is in hours (not minutes) before dividing.

  2. Question 262. Scenario: A newly hired nurse is transcribing an order and notices something that should be flagged. Order: (as written) "0.9% sodium chloride 1,000 mL IV at 125.0 mL/hr." Available: 1,000 mL bag of 0.9% sodium chloride. Question: Which element of this order violates The Joint Commission "Do Not Use" list, and how should the order be written correctly?

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    Correct answer: Trailing zero in "125.0 mL/hr"; write as "125 mL/hr" Setup (dimensional analysis): Not applicable (order-safety/notation review). Raw calculation: Not applicable. Rounding: Not applicable. Final answer: The order should read: "0.9% sodium chloride 1,000 mL IV at 125 mL/hr." Rationale: The Joint Commission "Do Not Use" list prohibits a trailing zero after a decimal point (e.g., "125.0") because the decimal point can be overlooked and the dose misread as "1250" (a 10-fold error). The correct form is a whole number without a trailing zero. Note that "1,000" with a comma is acceptable and is not on the list. Clinical pearl: Never write a trailing zero (X.0); always use a leading zero for decimals less than one (0.X). Both rules protect against 10-fold dosing errors.

  3. Question 263. Scenario: A 7-year-old child with mild dehydration is prescribed a maintenance bolus. Order: Infuse 250 mL 0.9% sodium chloride IV over 5 hours. Available: 250 mL bag of 0.9% sodium chloride; infusion pump. Question: At what rate (mL/hr) should the pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 50 mL/hr Setup (dimensional analysis): Rate = 250 mL ÷ 5 hr Raw calculation: 250 ÷ 5 = 50 Rounding: 50 is a whole number; no rounding needed. Final answer: 50 mL/hr Rationale: Dividing the total volume (250 mL) by the time (5 hours) gives the volume that must infuse each hour. Clinical pearl: Small pediatric volumes are often ordered as "total volume over total hours"; keep the mL/hr calculation identical regardless of bag size.

  4. Question 264. Scenario: An adult with gastroenteritis requires volume replacement. Order: Infuse 1,000 mL lactated Ringer's IV over 10 hours. Available: 1,000 mL bag of lactated Ringer's; infusion pump. Question: At what rate (mL/hr) should the pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 100 mL/hr Setup (dimensional analysis): Rate = 1,000 mL ÷ 10 hr Raw calculation: 1,000 ÷ 10 = 100 Rounding: 100 is a whole number; no rounding needed. Final answer: 100 mL/hr Rationale: A 1-liter bag infused over 10 hours delivers 100 mL each hour. Clinical pearl: A 1,000 mL bag at 100 mL/hr always runs 10 hours — a quick mental benchmark for many orders.

  5. Question 265. Scenario: A postoperative adult is receiving a dextrose-containing maintenance fluid. Order: Infuse 750 mL D5 ½ NS (5% dextrose and 0.45% sodium chloride) IV over 5 hours. Available: 750 mL bag of D5 ½ NS; infusion pump. Question: At what rate (mL/hr) should the pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 150 mL/hr Setup (dimensional analysis): Rate = 750 mL ÷ 5 hr Raw calculation: 750 ÷ 5 = 150 Rounding: 150 is a whole number; no rounding needed. Final answer: 150 mL/hr Rationale: The 750 mL bag divided evenly over 5 hours requires 150 mL/hr. Clinical pearl: Dextrose-containing fluids are not interchangeable with plain saline; verify the solution type matches the order before setting the rate.

  6. Question 266. Scenario: A patient needs a rapid small-volume IV medication flush. Order: Infuse 50 mL 0.9% sodium chloride IV over 30 minutes. Available: 50 mL of 0.9% sodium chloride; infusion pump. Question: At what rate (mL/hr) should the pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 100 mL/hr Setup (dimensional analysis): Convert minutes to hours first: 30 min = 0.5 hr. Rate = 50 mL ÷ 0.5 hr Raw calculation: 50 ÷ 0.5 = 100 Rounding: 100 is a whole number; no rounding needed. Final answer: 100 mL/hr Rationale: When the order is in minutes, convert to hours (30 min = 0.5 hr) before dividing. 50 mL over half an hour is the same rate as 100 mL over a full hour. Clinical pearl: To go from "mL over X minutes" to mL/hr, multiply by (60 ÷ X). Here, 50 mL × (60 ÷ 30) = 100 mL/hr.

  7. Question 267. Scenario: A patient is prescribed a medication diluted in a small IV bag to be infused over 45 minutes. Order: Infuse 100 mL 0.9% sodium chloride IV over 45 minutes. Available: 100 mL bag of 0.9% sodium chloride; infusion pump. Question: At what rate (mL/hr) should the pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 133 mL/hr Setup (dimensional analysis): Convert 45 min to hours: 45 min = 0.75 hr. Rate = 100 mL ÷ 0.75 hr Raw calculation: 100 ÷ 0.75 = 133.333… Rounding: The rule is nearest whole mL/hr; 133.333 rounds down to 133. Final answer: 133 mL/hr Rationale: 100 mL infused over three-quarters of an hour equals 133.33 mL/hr, which rounds to 133 mL/hr for pump setting. Clinical pearl: 45 minutes = 0.75 hr, not 0.45 hr — a common decimal-conversion error to watch for.

  8. Question 268. Scenario: An adult admitted with dehydration has a large-volume order written. Order: Infuse 1,500 mL 5% dextrose in water (D5W) IV over 12 hours. Available: D5W; infusion pump. Question: What rate (mL/hr) should the pump be set at? A) 100 mL/hr B) 115 mL/hr C) 125 mL/hr D) 150 mL/hr

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    Correct answer: C) 125 mL/hr Setup (dimensional analysis): Rate = 1,500 mL ÷ 12 hr Raw calculation: 1,500 ÷ 12 = 125 Rounding: 125 is a whole number; no rounding needed. Final answer: 125 mL/hr Rationale: 1,500 mL over 12 hours = 125 mL/hr. Distractor analysis: 100 mL/hr would require 15 hours; 150 mL/hr would finish in 10 hours; 115 mL/hr is a plausible midpoint error. Clinical pearl: Check your answer by multiplying back: 125 mL/hr × 12 hr = 1,500 mL. If the product doesn't equal the bag volume, re-check.

  9. Question 269. Scenario: A patient is receiving a modest maintenance infusion. Order: Infuse 275 mL D5W IV over 4 hours. Available: D5W; infusion pump calibrated in tenths of a mL/hr. Question: At what rate (mL/hr) should the pump be set? Round to the nearest tenth mL/hr.

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    Correct answer: 68.8 mL/hr Setup (dimensional analysis): Rate = 275 mL ÷ 4 hr Raw calculation: 275 ÷ 4 = 68.75 Rounding: The rule is nearest tenth mL/hr; 68.75 rounds up to 68.8. Final answer: 68.8 mL/hr Rationale: The pump is calibrated in tenths, so the raw result 68.75 is rounded to one decimal place. 68.75 lies exactly between 68.7 and 68.8 and rounds to 68.8 (round half up). Clinical pearl: State the rounding rule to match the device: whole numbers for standard pumps, tenths only when the pump supports and the order specifies tenths.

  10. Question 270. Scenario: An adult is placed on a 1-liter bag of dextrose solution. Order: Infuse 1 L D5W IV over 5 hours. Available: 1 L bag of D5W; infusion pump. Question: At what rate (mL/hr) should the pump be set? Round to the nearest whole mL/hr.

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    Correct answer: 200 mL/hr Setup (dimensional analysis): Convert 1 L to mL first: 1 L = 1,000 mL. Rate = 1,000 mL ÷ 5 hr Raw calculation: 1,000 ÷ 5 = 200 Rounding: 200 is a whole number; no rounding needed. Final answer: 200 mL/hr Rationale: The bag is 1 liter, which is exactly 1,000 mL. Dividing by 5 hours yields 200 mL/hr. Clinical pearl: Always convert liters to milliliters before computing mL/hr so the units cancel correctly (1 L = 1,000 mL).

  11. Question 271. Scenario: A patient's 1-liter infusion is running slower than intended, and the nurse must catch up without exceeding the prescribed finish time. Order: Infuse 1,000 mL 0.9% sodium chloride IV over 8 hours. Available: 1,000 mL bag of 0.9% sodium chloride; infusion pump. Question: The pump was mistakenly set at 100 mL/hr for the first 2 hours. To deliver the remaining volume by the 8-hour mark, what new rate (mL/hr) must be used for the remaining 6 hours? Round to the nearest whole mL/hr.

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    Correct answer: 133 mL/hr Setup (dimensional analysis):

    • Correct rate: 1,000 mL ÷ 8 hr = 125 mL/hr
    • Volume infused in first 2 hr: 100 mL/hr × 2 hr = 200 mL
    • Remaining volume: 1,000 mL − 200 mL = 800 mL
    • Remaining time: 8 hr − 2 hr = 6 hr
    • New rate: 800 mL ÷ 6 hr Raw calculation: 800 ÷ 6 = 133.333… Rounding: Nearest whole mL/hr; 133.333 rounds down to 133. Final answer: 133 mL/hr Rationale: After 2 hours at the wrong rate, only 200 mL has infused (100 short of the 250 mL that should have infused at 125 mL/hr). The remaining 800 mL must be delivered over the remaining 6 hours, requiring 133.33 → 133 mL/hr. Clinical pearl: When recalculating to "catch up," always subtract both the volume already infused and the time already elapsed before dividing.

  12. Question 272. Scenario: A patient on a medical-surgical unit has a gravity infusion (no pump available). Order: Infuse 1,000 mL 0.9% sodium chloride IV over 8 hours. Available: 1,000 mL bag; administration set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in drops per minute (gtt/min). Round to the nearest whole drop.

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    Correct answer: 31 gtt/min Setup (dimensional analysis): gtt/min = (volume mL × drop factor gtt/mL) ÷ (time in minutes). Time = 8 hr × 60 min/hr = 480 min. gtt/min = (1,000 mL × 15 gtt/mL) ÷ 480 min Raw calculation: (1,000 × 15) ÷ 480 = 15,000 ÷ 480 = 31.25 Rounding: Nearest whole drop; 31.25 rounds down to 31. Final answer: 31 gtt/min Rationale: The drop factor converts mL to drops. 1,000 mL × 15 gtt/mL = 15,000 drops over 480 minutes = 31.25, rounded to 31 drops per minute. Clinical pearl: Always convert hours to minutes in the denominator when calculating gtt/min; forgetting the ×60 is a frequent error.

  13. Question 273. Scenario: A patient requires a 10-hour gravity infusion of dextrose. Order: Infuse 1,000 mL D5W IV over 10 hours. Available: D5W; administration set with a drop factor of 20 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 33 gtt/min Setup (dimensional analysis): Time = 10 hr × 60 = 600 min. gtt/min = (1,000 mL × 20 gtt/mL) ÷ 600 min Raw calculation: 20,000 ÷ 600 = 33.333… Rounding: Nearest whole drop; 33.333 rounds down to 33. Final answer: 33 gtt/min Rationale: 1,000 mL × 20 gtt/mL = 20,000 drops over 600 minutes gives 33.33 gtt/min, rounded to 33. Clinical pearl: A drop factor of 20 (macrodrip) is common on standard adult tubing — always read the label on the set.

  14. Question 274. Scenario: A postoperative patient has a 500 mL gravity infusion ordered. Order: Infuse 500 mL 0.9% sodium chloride IV over 4 hours. Available: 500 mL bag; administration set with a drop factor of 10 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 21 gtt/min Setup (dimensional analysis): Time = 4 hr × 60 = 240 min. gtt/min = (500 mL × 10 gtt/mL) ÷ 240 min Raw calculation: 5,000 ÷ 240 = 20.833… Rounding: Nearest whole drop; 20.833 rounds up to 21. Final answer: 21 gtt/min Rationale: 500 mL × 10 gtt/mL = 5,000 drops over 240 minutes = 20.83, rounded to 21 gtt/min. Clinical pearl: A drop factor of 10 delivers larger drops, so fewer drops per minute are needed for the same mL/hr rate.

  15. Question 275. Scenario: An adult in the emergency department receives lactated Ringer's by gravity. Order: Infuse 1,000 mL lactated Ringer's IV over 6 hours. Available: 1,000 mL bag; administration set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 42 gtt/min Setup (dimensional analysis): Time = 6 hr × 60 = 360 min. gtt/min = (1,000 mL × 15 gtt/mL) ÷ 360 min Raw calculation: 15,000 ÷ 360 = 41.667… Rounding: Nearest whole drop; 41.667 rounds up to 42. Final answer: 42 gtt/min Rationale: 1,000 mL × 15 gtt/mL = 15,000 drops over 360 minutes = 41.67, rounded to 42 gtt/min. Clinical pearl: Count drops over a full minute for accuracy; a 15-second count multiplied by 4 is only an estimate.

  16. Question 276. Scenario: A critically ill adult needs a small volume delivered rapidly through a microdrip set. Order: Infuse 100 mL 0.9% sodium chloride IV over 30 minutes. Available: 100 mL bag; microdrip administration set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 200 gtt/min Setup (dimensional analysis): Time = 30 min (already in minutes). gtt/min = (100 mL × 60 gtt/mL) ÷ 30 min Raw calculation: 6,000 ÷ 30 = 200 Rounding: 200 is a whole number; no rounding needed. Final answer: 200 gtt/min Rationale: 100 mL × 60 gtt/mL = 6,000 drops over 30 minutes = 200 gtt/min. Because the microdrip factor is 60, gtt/min equals the mL/hr rate (100 mL over 30 min = 200 mL/hr = 200 gtt/min). Clinical pearl: On a microdrip (60 gtt/mL) set, gtt/min always equals mL/hr — a useful shortcut and cross-check.

  17. Question 277. Scenario: A patient is to receive an antibiotic mixed in 250 mL over 90 minutes by gravity. Order: Infuse 250 mL 0.9% sodium chloride (with antibiotic) IV over 90 minutes. Available: 250 mL bag; administration set with a drop factor of 20 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 56 gtt/min Setup (dimensional analysis): Time = 90 min. gtt/min = (250 mL × 20 gtt/mL) ÷ 90 min Raw calculation: 5,000 ÷ 90 = 55.556… Rounding: Nearest whole drop; 55.556 rounds up to 56. Final answer: 56 gtt/min Rationale: 250 mL × 20 gtt/mL = 5,000 drops over 90 minutes = 55.56, rounded to 56 gtt/min. Clinical pearl: When the infusion time is already given in minutes, use it directly in the denominator — no hour conversion needed.

  18. Question 278. Scenario: A patient receives a small-volume medication infusion over 20 minutes by gravity. Order: Infuse 50 mL 0.9% sodium chloride (with medication) IV over 20 minutes. Available: 50 mL bag; administration set with a drop factor of 15 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 38 gtt/min Setup (dimensional analysis): Time = 20 min. gtt/min = (50 mL × 15 gtt/mL) ÷ 20 min Raw calculation: 750 ÷ 20 = 37.5 Rounding: Nearest whole drop; 37.5 rounds up to 38. Final answer: 38 gtt/min Rationale: 50 mL × 15 gtt/mL = 750 drops over 20 minutes = 37.5, which rounds to 38 gtt/min (round half up). Clinical pearl: Small volumes over short times yield high gtt/min; double-check such rates carefully because a few drops either way is a large relative error.

  19. Question 279. Scenario: A patient has a 750 mL gravity infusion of a dextrose-saline solution. Order: Infuse 750 mL D5 NS (5% dextrose and 0.9% sodium chloride) IV over 5 hours. Available: 750 mL bag; administration set with a drop factor of 10 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 25 gtt/min Setup (dimensional analysis): Time = 5 hr × 60 = 300 min. gtt/min = (750 mL × 10 gtt/mL) ÷ 300 min Raw calculation: 7,500 ÷ 300 = 25 Rounding: 25 is a whole number; no rounding needed. Final answer: 25 gtt/min Rationale: 750 mL × 10 gtt/mL = 7,500 drops over 300 minutes = exactly 25 gtt/min. Clinical pearl: The drop factor multiplies the volume into drops; the larger the drop factor, the more drops per minute for the same volume/time.

  20. Question 280. Scenario: A patient has a 7-hour gravity infusion ordered. Order: Infuse 1,000 mL 0.9% sodium chloride IV over 7 hours. Available: 1,000 mL bag; administration set with a drop factor of 15 gtt/mL. Question: What flow rate (gtt/min) should be set? A) 21 gtt/min B) 35 gtt/min C) 36 gtt/min D) 42 gtt/min

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    Correct answer: C) 36 gtt/min Setup (dimensional analysis): Time = 7 hr × 60 = 420 min. gtt/min = (1,000 mL × 15 gtt/mL) ÷ 420 min Raw calculation: 15,000 ÷ 420 = 35.714… Rounding: Nearest whole drop; 35.714 rounds up to 36. Final answer: 36 gtt/min Rationale: 1,000 mL × 15 gtt/mL = 15,000 drops over 420 minutes = 35.71 → 36 gtt/min. Distractors: 35 (truncated, not rounded); 42 (used 6 hours instead of 7); 21 (used 12 hours or wrong factor). Clinical pearl: Round gtt/min to the nearest whole drop — drops cannot be fractional — but only after computing the full unrounded value.

  21. Question 281. Scenario: A patient is on a microdrip set for precise small-volume control. Order: Infuse 0.9% sodium chloride IV at 60 mL/hr. Available: Microdrip administration set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 60 gtt/min Setup (dimensional analysis): gtt/min = mL/hr × (drop factor ÷ 60). gtt/min = 60 mL/hr × (60 gtt/mL ÷ 60 min/hr) Raw calculation: 60 × 1 = 60 Rounding: 60 is a whole number; no rounding needed. Final answer: 60 gtt/min Rationale: On a 60 gtt/mL microdrip set, the gtt/min rate numerically equals the mL/hr rate because 60 drops = 1 mL and there are 60 minutes in an hour. So 60 mL/hr = 60 gtt/min. Clinical pearl: Microdrip shortcut: gtt/min = mL/hr. This makes microdrip ideal for slow, precise pediatric or critical-care infusions.

  22. Question 282. Scenario: A patient's maintenance rate is set at 125 mL/hr on a microdrip set. Order: Infuse 0.9% sodium chloride IV at 125 mL/hr. Available: Microdrip administration set with a drop factor of 60 gtt/mL. Question: Calculate the flow rate in gtt/min. Round to the nearest whole drop.

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    Correct answer: 125 gtt/min Setup (dimensional analysis): gtt/min = 125 mL/hr × (60 gtt/mL ÷ 60 min/hr) Raw calculation: 125 × 1 = 125 Rounding: 125 is a whole number; no rounding needed. Final answer: 125 gtt/min Rationale: With a microdrip set (60 gtt/mL), each mL/hr equals 1 gtt/min, so 125 mL/hr = 125 gtt/min. Clinical pearl: For microdrip, verify by the shortcut: gtt/min should always equal the ordered mL/hr.

  23. Question 283. Scenario: A nurse must document how long a bag of IV fluid will last. Order: Infuse 1,000 mL 0.9% sodium chloride IV at 125 mL/hr. Available: 1,000 mL bag; infusion pump. Question: How many hours will it take for the entire 1,000 mL to infuse?

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    Correct answer: 8 hours Setup (dimensional analysis): Time (hr) = total volume ÷ rate = 1,000 mL ÷ 125 mL/hr Raw calculation: 1,000 ÷ 125 = 8 Rounding: Not applicable (exact whole hours). Final answer: 8 hours Rationale: Dividing the total volume by the hourly rate gives the infusion duration. 1,000 mL at 125 mL/hr lasts exactly 8 hours. Clinical pearl: Infusion duration = volume ÷ rate; this is the inverse of the rate calculation (rate = volume ÷ time).

  24. Question 284. Scenario: A patient is receiving a 500 mL infusion at a slower maintenance rate. Order: Infuse 500 mL 0.9% sodium chloride IV at 75 mL/hr. Available: 500 mL bag; infusion pump. Question: How long will the infusion take? Express the answer in hours and minutes.

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    Correct answer: 6 hours 40 minutes Setup (dimensional analysis): Time (hr) = 500 mL ÷ 75 mL/hr Raw calculation: 500 ÷ 75 = 6.6667 hours. Whole hours = 6; remainder = 0.6667 hr × 60 min/hr = 40 min Rounding: Convert the decimal fraction of an hour to minutes; 0.6667 hr = 40 min. Final answer: 6 hours 40 minutes Rationale: 500 mL at 75 mL/hr takes 6⅔ hours. The 0.667-hour remainder equals 40 minutes (0.667 × 60 = 40). Clinical pearl: To convert a decimal hour to minutes, multiply the decimal part by 60 — 0.5 hr = 30 min, 0.25 hr = 15 min, etc.

  25. Question 285. Scenario: A patient has a 1-liter bag infusing at a fixed rate. Order: Infuse 1,000 mL D5W IV at 80 mL/hr. Available: 1,000 mL bag; infusion pump. Question: How long will the infusion take? Express the answer in hours and minutes.

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    Correct answer: 12 hours 30 minutes Setup (dimensional analysis): Time (hr) = 1,000 mL ÷ 80 mL/hr Raw calculation: 1,000 ÷ 80 = 12.5 hours = 12 hours + 0.5 hr × 60 = 30 min Rounding: Not applicable (0.5 hr is an exact half hour). Final answer: 12 hours 30 minutes Rationale: 1,000 mL at 80 mL/hr takes 12.5 hours, i.e., 12 hours 30 minutes. Clinical pearl: A decimal like 12.5 hours means 12 hours and 30 minutes — not 12 hours and 5 minutes.

  26. Question 286. Scenario: A patient receives a 250 mL infusion at a slow rate. Order: Infuse 250 mL 0.9% sodium chloride IV at 60 mL/hr. Available: 250 mL bag; infusion pump. Question: How long will the infusion take? Express the answer in hours and minutes.

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    Correct answer: 4 hours 10 minutes Setup (dimensional analysis): Time (hr) = 250 mL ÷ 60 mL/hr Raw calculation: 250 ÷ 60 = 4.1667 hours = 4 hours + 0.1667 hr × 60 = 10 min Rounding: Convert the decimal fraction to minutes; 0.1667 hr ≈ 10 min. Final answer: 4 hours 10 minutes Rationale: 250 mL at 60 mL/hr takes 4.167 hours, which is 4 hours plus 0.167 × 60 ≈ 10 minutes. Clinical pearl: Use the exact decimal before converting to minutes; rounding the hours too early (e.g., to 4.2) distorts the minute total.

  27. Question 287. Scenario: A pediatric patient has a small-volume infusion ordered. Order: Infuse 100 mL 0.9% sodium chloride IV at 80 mL/hr. Available: 100 mL bag; infusion pump. Question: How long will the infusion take? Express the answer in hours and minutes.

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    Correct answer: 1 hour 15 minutes Setup (dimensional analysis): Time (hr) = 100 mL ÷ 80 mL/hr Raw calculation: 100 ÷ 80 = 1.25 hours = 1 hour + 0.25 hr × 60 = 15 min Rounding: Not applicable (0.25 hr is an exact quarter hour). Final answer: 1 hour 15 minutes Rationale: 100 mL at 80 mL/hr takes 1.25 hours = 1 hour 15 minutes. Clinical pearl: 0.25 hour = 15 minutes, 0.75 hour = 45 minutes — memorize the common quarter-hour fractions.

  28. Question 288. Scenario: A nurse hangs a 1-liter bag and needs to determine when it will finish. Order: Infuse 1,000 mL 0.9% sodium chloride IV at 125 mL/hr, starting at 0800. Available: 1,000 mL bag; infusion pump. Question: At what time (military time) will the infusion be complete?

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    Correct answer: 1600 Setup (dimensional analysis): Duration = 1,000 mL ÷ 125 mL/hr = 8 hr. Completion time = 0800 + 8 hr = 1600 Raw calculation: 0800 + 0800 = 1600 Rounding: Not applicable. Final answer: 1600 (4:00 PM) Rationale: The 1,000 mL bag runs 8 hours at 125 mL/hr, so it finishes at 1600. Clinical pearl: Add the duration to the start time in military time; when the total passes 2359, subtract 24 hours and note the next day.

  29. Question 289. Scenario: A patient's 500 mL infusion was started in the early afternoon. Order: Infuse 500 mL 0.9% sodium chloride IV at 75 mL/hr, starting at 1400. Available: 500 mL bag; infusion pump. Question: At what time (military time) will the infusion be complete?

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    Correct answer: 2040 Setup (dimensional analysis): Duration = 500 mL ÷ 75 mL/hr = 6.6667 hr = 6 hr 40 min. Completion = 1400 + 6 hr 40 min = 2040 Raw calculation: 1400 + 6:40 = 2040 Rounding: Not applicable. Final answer: 2040 (8:40 PM) Rationale: The 500 mL bag runs 6 hours 40 minutes at 75 mL/hr, finishing at 2040. Clinical pearl: Add hours and minutes separately (1400 + 6 hr = 2000, then + 40 min = 2040) to avoid carry errors.

  30. Question 290. Scenario: A patient's 1-liter infusion is started mid-morning. Order: Infuse 1,000 mL D5W IV at 100 mL/hr, starting at 0930. Available: 1,000 mL bag; infusion pump. Question: At what time (military time) will the infusion be complete?

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    Correct answer: 1930 Setup (dimensional analysis): Duration = 1,000 mL ÷ 100 mL/hr = 10 hr. Completion = 0930 + 10 hr = 1930 Raw calculation: 0930 + 1000 = 1930 Rounding: Not applicable. Final answer: 1930 (7:30 PM) Rationale: The 1-liter bag runs 10 hours at 100 mL/hr, so it completes at 1930. Clinical pearl: 1,000 mL at 100 mL/hr is always a 10-hour infusion — a fast way to sanity-check completion times.

  31. Question 291. Scenario: A patient's 250 mL infusion is started late in the evening. Order: Infuse 250 mL 0.9% sodium chloride IV at 60 mL/hr, starting at 2230. Available: 250 mL bag; infusion pump. Question: At what time (military time) will the infusion be complete? Note whether the time is the same day or the next day.

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    Correct answer: 0240 the next day Setup (dimensional analysis): Duration = 250 mL ÷ 60 mL/hr = 4.1667 hr = 4 hr 10 min. Completion = 2230 + 4 hr 10 min = 2640 → 2640 − 2400 = 0240 (next day) Raw calculation: 2230 + 4:10 = 2640; 2640 − 2400 = 0240 Rounding: Not applicable. Final answer: 0240 the next day Rationale: The 250 mL bag runs 4 hours 10 minutes. Adding to 2230 passes midnight (2400), so the finish time rolls to 0240 on the following day. Clinical pearl: Any completion time greater than 2359 crosses midnight — subtract 2400 and document the date change.

  32. Question 292. Scenario: A patient's 1-liter infusion is started early in the morning. Order: Infuse 1,000 mL 0.9% sodium chloride IV at 80 mL/hr, starting at 0615. Available: 1,000 mL bag; infusion pump. Question: At what time will the infusion be complete? A) 1815 B) 1830 C) 1845 D) 1900

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    Correct answer: C) 1845 Setup (dimensional analysis): Duration = 1,000 mL ÷ 80 mL/hr = 12.5 hr = 12 hr 30 min. Completion = 0615 + 12 hr 30 min = 1845 Raw calculation: 0615 + 12:00 = 1815; + 0:30 = 1845 Rounding: Not applicable. Final answer: 1845 (6:45 PM) Rationale: At 80 mL/hr the 1-liter bag runs 12.5 hours, finishing at 1845. Distractors: 1815 (dropped the 30 minutes); 1830 (miscalculated the fraction); 1900 (rounded the duration incorrectly). Clinical pearl: Don't lose the fractional hour — 12.5 hours adds 30 minutes, not zero, to the start time.

  33. Question 293. Scenario: A nurse checks a 1-liter infusion that has been running for 3 hours. Order: Infuse 1,000 mL 0.9% sodium chloride IV at 125 mL/hr. Available: 1,000 mL bag; infusion pump. Question: After 3 hours, how many mL have infused, and how many mL remain in the bag?

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    Correct answer: 375 mL infused; 625 mL remaining Setup (dimensional analysis): Volume infused = rate × time = 125 mL/hr × 3 hr = 375 mL. Remaining = 1,000 mL − 375 mL = 625 mL Raw calculation: 125 × 3 = 375; 1,000 − 375 = 625 Rounding: Not applicable (whole mL). Final answer: 375 mL infused; 625 mL remaining Rationale: Multiplying the rate by elapsed time gives the volume already delivered. Subtracting that from the bag volume gives what remains. Clinical pearl: "Volume infused = rate × time" is the same relationship as "distance = speed × time" — apply it both directions.

  34. Question 294. Scenario: A 500 mL infusion was started at 0800 and the nurse checks it at 1100. Order: Infuse 500 mL 0.9% sodium chloride IV at 100 mL/hr, starting at 0800. Available: 500 mL bag; infusion pump. Question: At 1100, how many mL remain in the bag?

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    Correct answer: 200 mL remaining Setup (dimensional analysis): Elapsed time = 1100 − 0800 = 3 hr. Infused = 100 mL/hr × 3 hr = 300 mL. Remaining = 500 mL − 300 mL = 200 mL Raw calculation: 100 × 3 = 300; 500 − 300 = 200 Rounding: Not applicable (whole mL). Final answer: 200 mL remaining Rationale: From 0800 to 1100 is 3 hours, during which 300 mL infuses. The 500 mL bag has 200 mL left. Clinical pearl: Always compute elapsed time from the actual start time, not from when the nurse arrived on shift.

  35. Question 295. Scenario: A nurse checks a 1-liter infusion that has been running for 5 hours. Order: Infuse 1,000 mL 0.9% sodium chloride IV at 125 mL/hr. Available: 1,000 mL bag; infusion pump. Question: After 5 hours, how many mL remain in the bag?

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    Correct answer: 375 mL remaining Setup (dimensional analysis): Infused = 125 mL/hr × 5 hr = 625 mL. Remaining = 1,000 mL − 625 mL = 375 mL Raw calculation: 125 × 5 = 625; 1,000 − 625 = 375 Rounding: Not applicable (whole mL). Final answer: 375 mL remaining Rationale: After 5 hours at 125 mL/hr, 625 mL has infused, leaving 375 mL in the 1-liter bag. Clinical pearl: At 125 mL/hr, a 1-liter bag is half empty at the 4-hour mark and three-quarters empty at 6 hours — useful landmarks for anticipating bag changes.

  36. Question 296. Scenario: A 250 mL infusion has been running for 90 minutes. Order: Infuse 250 mL 0.9% sodium chloride IV at 60 mL/hr. Available: 250 mL bag; infusion pump. Question: After 90 minutes, how many mL remain in the bag?

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    Correct answer: 160 mL remaining Setup (dimensional analysis): Convert 90 min to hours: 90 min = 1.5 hr. Infused = 60 mL/hr × 1.5 hr = 90 mL. Remaining = 250 mL − 90 mL = 160 mL Raw calculation: 60 × 1.5 = 90; 250 − 90 = 160 Rounding: Not applicable (whole mL). Final answer: 160 mL remaining Rationale: 90 minutes equals 1.5 hours; at 60 mL/hr that infuses 90 mL, leaving 160 mL in the 250 mL bag. Clinical pearl: Convert minutes to hours before multiplying by an hourly rate (90 min = 1.5 hr, not 0.9 hr).

  37. Question 297. Scenario: A nurse assesses whether a gravity-controlled pump infusion is on schedule. Order: Infuse 1,000 mL 0.9% sodium chloride IV over 8 hours. Available: 1,000 mL bag; infusion pump. Question: At the 2-hour mark, 700 mL remain in the bag. Is the infusion ahead of schedule, on schedule, or behind schedule, and by how many mL?

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    Correct answer: Ahead of schedule by 50 mL Setup (dimensional analysis):

    • Ordered rate: 1,000 mL ÷ 8 hr = 125 mL/hr
    • Expected infused by 2 hr: 125 mL/hr × 2 hr = 250 mL
    • Expected remaining: 1,000 mL − 250 mL = 750 mL
    • Actual remaining: 700 mL → actual infused = 1,000 − 700 = 300 mL
    • Difference: 300 mL − 250 mL = 50 mL ahead Raw calculation: 125 × 2 = 250; 1,000 − 250 = 750; 1,000 − 700 = 300; 300 − 250 = 50 Rounding: Not applicable. Final answer: Ahead of schedule by 50 mL Rationale: Only 750 mL should remain at the 2-hour mark, but 700 mL remain, meaning 300 mL has infused instead of the expected 250 mL — 50 mL more than expected, so the infusion is 50 mL ahead of schedule. Clinical pearl: To judge schedule, compare actual remaining volume to the volume that should remain (rate × elapsed time subtracted from total).

  38. Question 298. Scenario: A nurse discovers an infusion is running behind and must recalculate the rate to finish on time. Order: Infuse 1,000 mL 0.9% sodium chloride IV over 8 hours. Available: 1,000 mL bag; infusion pump. Question: At the 4-hour mark, 550 mL remain in the bag. Is the infusion ahead or behind schedule, and by how many mL? What new rate (mL/hr) should be set to finish the remaining volume by the 8-hour mark? Round to the nearest whole mL/hr.

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    Correct answer: Behind schedule by 50 mL; new rate 138 mL/hr Setup (dimensional analysis):

    • Ordered rate: 1,000 mL ÷ 8 hr = 125 mL/hr
    • Expected infused by 4 hr: 125 mL/hr × 4 hr = 500 mL
    • Expected remaining: 1,000 mL − 500 mL = 500 mL
    • Actual remaining: 550 mL → actual infused = 1,000 − 550 = 450 mL
    • Behind by: 500 mL − 450 mL = 50 mL
    • Remaining volume: 550 mL; remaining time: 8 hr − 4 hr = 4 hr
    • New rate: 550 mL ÷ 4 hr Raw calculation: 125 × 4 = 500; 1,000 − 500 = 500; 1,000 − 550 = 450; 500 − 450 = 50; 550 ÷ 4 = 137.5 Rounding: Nearest whole mL/hr; 137.5 rounds up to 138. Final answer: Behind schedule by 50 mL; new rate 138 mL/hr Rationale: At the 4-hour mark only 450 mL has infused (should be 500 mL), leaving 550 mL — 50 mL behind. To finish the remaining 550 mL in the remaining 4 hours, the pump must run at 137.5 → 138 mL/hr. Clinical pearl: When a rate change is needed, recompute using the actual remaining volume and actual remaining time, never the original total.

  39. Question 299. Scenario: A patient receives a continuous dextrose infusion throughout the day shift. Order: Infuse D5W IV at 80 mL/hr for 12 hours. Available: D5W; infusion pump. Question: What total volume (mL) will the patient receive over the 12 hours?

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    Correct answer: 960 mL Setup (dimensional analysis): Total volume = rate × time = 80 mL/hr × 12 hr Raw calculation: 80 × 12 = 960 Rounding: Not applicable (whole mL). Final answer: 960 mL Rationale: Multiplying the fixed hourly rate by the total hours gives the total volume delivered: 80 mL/hr for 12 hours equals 960 mL. Clinical pearl: "Rate × time = total volume" lets you back-calculate total intake for shift documentation and fluid-balance records.

  40. Question 300. Scenario: A patient requires two consecutive 1-liter bags of IV fluid. Order: Infuse 1,000 mL 0.9% sodium chloride IV at 125 mL/hr, starting at 0800; when complete, infuse a second 1,000 mL bag of 0.9% sodium chloride at the same rate. Available: Two 1,000 mL bags of 0.9% sodium chloride; infusion pump. Question: At what time (military time) will the second bag be complete, and what total volume will the patient receive over the entire infusion?

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    Correct answer: 2400 (midnight); total volume 2,000 mL Setup (dimensional analysis):

    • Duration per bag: 1,000 mL ÷ 125 mL/hr = 8 hr
    • First bag completes: 0800 + 8 hr = 1600
    • Second bag completes: 1600 + 8 hr = 2400
    • Total volume: 1,000 mL × 2 = 2,000 mL Raw calculation: 1,000 ÷ 125 = 8; 0800 + 8 = 1600; 1600 + 8 = 2400; 1,000 × 2 = 2,000 Rounding: Not applicable. Final answer: 2400 (midnight); 2,000 mL total Rationale: Each 1-liter bag runs 8 hours at 125 mL/hr. The first finishes at 1600 and the second finishes 8 hours later at 2400. Together the patient receives 2,000 mL over 16 hours. Clinical pearl: For sequential bags, add each bag's duration to the previous completion time, and sum the volumes for total intake.

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