1.Easy
Practice exercise (made-up values, not clinical guidance). 10 g of potassium chloride is dissolved in water to a total volume of 100 mL. What is the percentage strength p (% w/v)?
10 g100 mL
p = %
Pharmacy calculations worksheet with answers
2.Easy
A solution is 5% w/v. You need 150 mg of the drug. Draw up the volume in the syringe: what volume V is that?
5% w/v150 mg
V = mL
3.Medium
Practice exercise (made-up values, not clinical guidance). A vial of penicillin G contains 5 000 000 units. Its practice label gives three strengths (see the table). You add 3.2 mL of diluent. The prescribed dose is 1 500 000 units. What volume V do you draw up? Round to one decimal place.
3.2 mL → 1 000 000 units/mL1 500 000 units
V = mL
4.Medium
A solution has a ratio strength of 1:1000. You need 0.94 mg. Draw up the volume in the 1 mL syringe: what volume V is that?
1:10000.94 mg
V = mL
5.Hard
A vial holds 1000 mg of powder. You add 4.8 mL of diluent, and the powder adds 0.2 mL of volume. The prescription is 820 mg. Draw up the dose: what volume V do you give?
1000 mg4.8 mL + 0.2 mL820 mg
V = mL
6.Hard
Practice exercise (made-up values, not clinical guidance). You must prepare 300 mL of 30% dextrose by mixing 70% and 10% dextrose. How many mL V of the 70% solution do you need? Round to the nearest whole mL.
70%10%30%300 mL
V = mL
Answer key
- 1. p = 10 %
- 2. V = 3 mL
- 3. V = 1.5 mL
- 4. V = 0.94 mL
- 5. V = 4.1 mL
- 6. V = 100 mL
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