A dose of 50 mg is ordered. The solution is 25 mg per 5 mL. How many milliliters are required?

A dose of 50 mg is ordered. The solution is 25 mg per 5 mL. How many milliliters are required?

• A. 10 mL
• B. 5 mL
• C. 7 mL
• D. 12 mL

Answer: (A)

Converting a prescribed dose into the volume of liquid using the solution’s concentration. The solution has 25 mg in 5 mL, which is 5 mg per 1 mL. To deliver 50 mg, use the relation 5 mg/mL × x mL = 50 mg, so x = 50 / 5 = 10 mL. You can also see this with a proportion: 25 mg/5 mL = 50 mg/x mL leads to x = 10 mL. Since the dose doubles from 25 mg to 50 mg, the required volume doubles from 5 mL to 10 mL. Therefore, 10 mL is needed.

Converting a prescribed dose into the volume of liquid using the solution’s concentration. The solution has 25 mg in 5 mL, which is 5 mg per 1 mL. To deliver 50 mg, use the relation 5 mg/mL × x mL = 50 mg, so x = 50 / 5 = 10 mL. You can also see this with a proportion: 25 mg/5 mL = 50 mg/x mL leads to x = 10 mL. Since the dose doubles from 25 mg to 50 mg, the required volume doubles from 5 mL to 10 mL. Therefore, 10 mL is needed.