If a dose is 30 mg, how many milliliters are needed given the concentration is 15 mg per mL?

If a dose is 30 mg, how many milliliters are needed given the concentration is 15 mg per mL?

• A. 4 mL
• B. 1 mL
• C. 2 mL
• D. 3 mL

Answer: (C)

Dose-to-volume conversion using concentration is what's being tested. Use Volume = Dose ÷ Concentration. Here, 30 mg divided by 15 mg per mL equals 2 mL. That means 2 mL of the solution contains 30 mg, since 2 mL × 15 mg/mL = 30 mg. If you used 1 mL, you’d deliver 15 mg; 3 mL would deliver 45 mg; 4 mL would deliver 60 mg. So the required volume is 2 mL.

Dose-to-volume conversion using concentration is what's being tested. Use Volume = Dose ÷ Concentration. Here, 30 mg divided by 15 mg per mL equals 2 mL. That means 2 mL of the solution contains 30 mg, since 2 mL × 15 mg/mL = 30 mg. If you used 1 mL, you’d deliver 15 mg; 3 mL would deliver 45 mg; 4 mL would deliver 60 mg. So the required volume is 2 mL.