A dose of 60 mg is prescribed. The solution is 10 mg/mL. How many milliliters are required?

A dose of 60 mg is prescribed. The solution is 10 mg/mL. How many milliliters are required?

• A. 4 mL
• B. 6 mL
• C. 8 mL
• D. 10 mL

Answer: (B)

When you need to find the volume from a prescribed dose and a solution’s strength, use Volume = Dose / Concentration. Here, the dose is 60 mg and the concentration is 10 mg per mL. So the volume is 60 mg ÷ 10 mg/mL = 6 mL. The units mg cancel, leaving mL, which makes sense because you’re measuring how many milliliters contain 60 mg. A quick check: 6 mL at 10 mg/mL delivers 6 × 10 = 60 mg, matching the prescribed dose. If you used 4, 8, or 10 mL, you’d get 40 mg, 80 mg, or 100 mg, respectively, which don’t match the dose.

When you need to find the volume from a prescribed dose and a solution’s strength, use Volume = Dose / Concentration. Here, the dose is 60 mg and the concentration is 10 mg per mL. So the volume is 60 mg ÷ 10 mg/mL = 6 mL. The units mg cancel, leaving mL, which makes sense because you’re measuring how many milliliters contain 60 mg.

A quick check: 6 mL at 10 mg/mL delivers 6 × 10 = 60 mg, matching the prescribed dose. If you used 4, 8, or 10 mL, you’d get 40 mg, 80 mg, or 100 mg, respectively, which don’t match the dose.