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Med math · 5 free problems

Drip rate practice: drops per minute with a drop factor

Drops per minute needs the time in minutes and the drop factor printed on the tubing. Round only the final answer, and only when the exercise says so.

Fictional labels. Round as each question says. How to round

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Drip rates: work through the set

Question 1 of 5

Drops per minute with a stated drop factor

In a gravity-infusion math exercise, 385 mL is to run over 3 hours. The supplied practice tubing label states 20 drops per mL. Calculate drops per minute (gtt/min). Use 60 minutes = 1 hour. Round only the final answer to the nearest whole drop per minute.

Worked solution and answer

Answer: 43 gtt/min.

(385 mL / 3 hours) × (20 drops / 1 mL) × (1 hour / 60 minutes) = 385/9 drops/minute = 42.777… drops/minute. Round to 43 drops/minute.

Check: Using the unrounded rate, (385/9 drops/minute) × 180 minutes ÷ 20 drops/mL = 385 mL. Rounding changes the calculated volume slightly. The drop factor is supplied by this problem; do not assume every tubing set has the same factor.

If you got about 2,567: That is the unrounded rate in drops per hour. Convert hours to minutes before giving gtt/min.

Question 2 of 5

Round a macrodrip rate

In a gravity-infusion math exercise, 1,000 mL is to run over 8 hours. The supplied practice tubing label states 15 drops per mL. Calculate drops per minute (gtt/min). Use 60 minutes = 1 hour. Round only the final answer to the nearest whole drop per minute.

Worked solution and answer

Answer: 31 gtt/min.

(1,000 mL / 480 minutes) × (15 drops / 1 mL) = 31.25 drops/minute. Round to 31 drops/minute.

Check: Using the unrounded rate, 31.25 drops/minute × 480 minutes ÷ 15 drops/mL = 1,000 mL.

If you got 1,875: That is drops per hour. Convert hours to minutes before dividing.

Question 3 of 5

An exact drip rate

In a gravity-infusion math exercise, 120 mL is to run over 60 minutes. The supplied practice tubing label states 10 drops per mL. Calculate drops per minute (gtt/min). Give the exact answer; no rounding is needed.

Worked solution and answer

Answer: 20 gtt/min.

(120 mL / 60 minutes) × (10 drops / 1 mL) = 20 drops/minute.

Check: 20 drops/minute × 60 minutes ÷ 10 drops/mL = 120 mL.

If you got 2: That is mL per minute. Multiply by the drop factor to reach drops per minute.

Question 4 of 5

Microdrip tubing

In a gravity-infusion math exercise, 50 mL is to run over 20 minutes. The supplied practice tubing label states 60 drops per mL. Calculate drops per minute (gtt/min). Give the exact answer; no rounding is needed.

Worked solution and answer

Answer: 150 gtt/min.

(50 mL / 20 minutes) × (60 drops / 1 mL) = 150 drops/minute. With a 60 drops/mL factor and a time in minutes, the mL/hour rate and the gtt/min rate are the same number.

Check: 150 drops/minute × 20 minutes ÷ 60 drops/mL = 50 mL.

If you got 2.5: That is mL per minute. Multiply by the 60 drops/mL factor.

Question 5 of 5

Round up at two thirds

In a gravity-infusion math exercise, 500 mL is to run over 4 hours. The supplied practice tubing label states 20 drops per mL. Calculate drops per minute (gtt/min). Use 60 minutes = 1 hour. Round only the final answer to the nearest whole drop per minute.

Worked solution and answer

Answer: 42 gtt/min.

(500 mL / 240 minutes) × (20 drops / 1 mL) = 41.666… drops/minute. Round to 42 drops/minute.

Check: Using the unrounded rate, (41.666… drops/minute) × 240 minutes ÷ 20 drops/mL = 500 mL.

If you got 2,500: That is drops per hour. Convert the 4 hours to 240 minutes first.

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