Using a burette with 20 drops/mL, how many drops per minute are needed to deliver 60 mL in 30 minutes?

Using a burette with 20 drops/mL, how many drops per minute are needed to deliver 60 mL in 30 minutes?

• A. 30 gtt/min
• B. 35 gtt/min
• C. 38 gtt/min
• D. 40 gtt/min

Answer: (D)

Calculating the required rate involves converting the volume into drops and then spreading that amount over the time window. The burette delivers 20 drops per milliliter, so delivering 60 mL requires 60 × 20 = 1200 drops in total. Over 30 minutes, the necessary rate is 1200 drops ÷ 30 minutes = 40 drops per minute. Therefore, the infusion should proceed at 40 gtt/min. If you plug in other rates, you’d get different total volumes in 30 minutes (for example, 30 gtt/min gives 900 drops, which is 45 mL; 35 gtt/min gives 1050 drops, which is 52.5 mL; 38 gtt/min gives 1140 drops, which is 57 mL). Only 40 gtt/min yields the full 60 mL in 30 minutes.

Calculating the required rate involves converting the volume into drops and then spreading that amount over the time window. The burette delivers 20 drops per milliliter, so delivering 60 mL requires 60 × 20 = 1200 drops in total. Over 30 minutes, the necessary rate is 1200 drops ÷ 30 minutes = 40 drops per minute. Therefore, the infusion should proceed at 40 gtt/min. If you plug in other rates, you’d get different total volumes in 30 minutes (for example, 30 gtt/min gives 900 drops, which is 45 mL; 35 gtt/min gives 1050 drops, which is 52.5 mL; 38 gtt/min gives 1140 drops, which is 57 mL). Only 40 gtt/min yields the full 60 mL in 30 minutes.