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Med math · 5 free problems

IV flow rate practice: mL per hour

A pump rate is volume divided by time in hours. Convert minutes before you divide, and when the exercise gives an amount per hour, find the bag's concentration first.

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

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IV flow rates: work through the set

Question 1 of 5

Volume per hour

In an infusion-math exercise, 750 mL is to run over 6 hours. What is the calculated rate in mL/hour? Give the exact answer; no rounding is needed. Calculate the rate from the supplied values without judging an actual patient's fluid needs.

Worked solution and answer

Answer: 125 mL/hour.

750 mL ÷ 6 hours = 125 mL/hour.

Check: 125 mL/hour × 6 hours = 750 mL.

If you got 4,500: Multiplying volume by time produces mL·hours, not mL/hour. Divide by time to find the amount delivered each hour.

Question 2 of 5

Convert minutes before finding mL/hour

In an infusion-math exercise, 90 mL is to run over 45 minutes. What is the calculated rate in mL/hour? Use 60 minutes = 1 hour. Give the exact answer; no rounding is needed.

Worked solution and answer

Answer: 120 mL/hour.

(90 mL / 45 minutes) × (60 minutes / 1 hour) = 120 mL/hour. Minutes cancel.

Check: 45 minutes = 0.75 hour; 120 mL/hour × 0.75 hour = 90 mL.

If you got 2 mL/hour: 90 ÷ 45 = 2 is the rate in mL/minute. Multiply by 60 to express that rate per hour.

Question 3 of 5

A liter over eight hours

In an infusion-math exercise, 1,000 mL is to run over 8 hours. What is the calculated rate in mL/hour? Give the exact answer; no rounding is needed. Calculate from the supplied values without judging an actual patient's fluid needs.

Worked solution and answer

Answer: 125 mL/hour.

1,000 mL ÷ 8 hours = 125 mL/hour.

Check: 125 mL/hour × 8 hours = 1,000 mL.

If you got 8,000: Multiplying volume by hours gives mL·hours. Divide the volume by the time.

Question 4 of 5

A short infusion in minutes

In an infusion-math exercise, 250 mL is to run over 30 minutes. What is the calculated rate in mL/hour? Use 60 minutes = 1 hour. Give the exact answer; no rounding is needed.

Worked solution and answer

Answer: 500 mL/hour.

(250 mL / 30 minutes) × (60 minutes / 1 hour) = 500 mL/hour. Minutes cancel.

Check: 30 minutes = 0.5 hour; 500 mL/hour × 0.5 hour = 250 mL.

If you got 8.33: That is mL per minute. Multiply by 60 to express the rate per hour.

Question 5 of 5

From mg per hour to mL per hour

In an infusion-math exercise, a practice bag is labeled 500 mg in 250 mL. The exercise specifies 20 mg/hour. What pump rate in mL/hour delivers that amount? Give the exact answer; no rounding is needed. Use only the supplied exercise values.

Worked solution and answer

Answer: 10 mL/hour.

Concentration: 500 mg ÷ 250 mL = 2 mg/mL. Rate: (20 mg/hour) × (1 mL / 2 mg) = 10 mL/hour. The mg units cancel.

Check: 10 mL/hour × 2 mg/mL = 20 mg/hour.

If you got 40: You multiplied 20 by the concentration instead of dividing by it. Each mL carries 2 mg, so fewer mL are needed than mg.

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