A nurse is preparing to infuse 500 ml of 0.

To calculate the flow rate in drops per minute (gtt/min), use the formula:

Flow rate (gtt/min) = (Total volume (ml) × Drop factor (gtt/ml)) / Time (minutes)

Given:

Total volume = 500 ml

Drop factor = 15 gtt/ml

Time = 4 hours (240 minutes)

Flow rate (gtt/min) = (500 ml × 15 gtt/ml) / 240 minutes = 7500 gtt / 240 minutes = 31.25 gtt/min

Rounded to the nearest whole number, the flow rate is 32 drops/minute.