1.Easy
Practice exercise (made-up values, not clinical guidance). 25 g of potassium chloride is dissolved in water to a total volume of 500 mL. What is the percentage strength p (% w/v)?
25 g500 mL
p = %
Pharmacy calculations worksheet with answers
2.Easy
A solution is 1% w/v. You need 34 mg of the drug. Draw up the volume in the syringe: what volume V is that?
1% w/v34 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 18.2 mL of diluent. The prescribed dose is 2 000 000 units. What volume V do you draw up? Round to one decimal place.
18.2 mL → 250 000 units/mL2 000 000 units
V = mL
4.Medium
A solution has a ratio strength of 1:1000. You need 0.75 mg. Draw up the volume in the 1 mL syringe: what volume V is that?
1:10000.75 mg
V = mL
5.Hard
Practice exercise (made-up values, not clinical guidance). You must prepare 1500 mL of 20% dextrose by mixing 50% and 5% dextrose. How many mL V of the 5% solution do you need? Round to the nearest whole mL.
50%5%20%1500 mL
V = mL
6.Hard
A vial holds 250 mg of powder. You add 9.8 mL of diluent, and the powder adds 0.2 mL of volume. The prescription is 62.5 mg. Draw up the dose: what volume V do you give?
250 mg9.8 mL + 0.2 mL62.5 mg
V = mL
Answer key
- 1. p = 5 %
- 2. V = 3.4 mL
- 3. V = 8 mL
- 4. V = 0.75 mL
- 5. V = 1000 mL
- 6. V = 2.5 mL
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