HESI A2 Math Practice Questions with Explanations
8 min read · Updated
HESI math is not conceptually hard. It is arithmetic, ratios, conversions and dosage calculation. What makes it a problem is that fifty questions in fifty minutes leaves no room for a slip, and dosage questions punish a misplaced decimal severely.
The exam allows an on-screen calculator, so the skill being tested is setting the problem up correctly, not arithmetic speed.
Question 1 — dosage calculation
A doctor orders 750 mg of a medication. The pharmacy supplies it at 250 mg per 5 mL. How many millilitres should be given?
- A10 mL
- B12.5 mL
- C15 mL
- D18 mL
Explanation
Use the formula: (dose wanted ÷ dose on hand) × volume on hand. That is (750 ÷ 250) × 5 = 3 × 5 = 15 mL. The most common error is dividing the other way round — 250 ÷ 750 — which gives 1.67 and an answer that is not offered, which is itself a useful check. If your answer is not among the options, you have almost always inverted the fraction.
Question 2 — unit conversion
A patient weighs 154 pounds. What is their weight in kilograms?
- A66 kg
- B70 kg
- C74 kg
- D78 kg
Explanation
One kilogram is 2.2 pounds, so divide: 154 ÷ 2.2 = 70 kg. Weight conversions appear constantly because paediatric dosing is calculated per kilogram, so an error here propagates into every calculation that follows. Learn the direction: pounds to kilograms divides, kilograms to pounds multiplies. A kilogram is heavier, so the number of kilograms must be smaller.
Question 3 — weight-based dosing
A medication is ordered at 5 mg per kilogram per day, divided into two equal doses. The patient weighs 40 kg. How much is given in each dose?
- A100 mg
- B125 mg
- C200 mg
- D400 mg
Explanation
The daily total is 5 × 40 = 200 mg. Divided into two equal doses, each dose is 100 mg. The trap is 200 mg — the correct daily total, but the question asked for the individual dose. Read the final sentence of a dosage question twice; the arithmetic is rarely where these are lost.
Underline what is being asked
Per dose or per day. Millilitres or milligrams. The distractors on these questions are built from correct intermediate answers, so getting the math right is not enough on its own.
Question 4 — ratio and proportion
A solution is mixed at a ratio of 3 parts concentrate to 7 parts water. How much concentrate is in 250 mL of the finished solution?
- A50 mL
- B75 mL
- C100 mL
- D107 mL
Explanation
The ratio 3:7 makes ten parts in total, so concentrate is 3/10 of the mixture. 250 × 0.3 = 75 mL. The usual mistake is treating 3:7 as 3/7 of the total, which gives about 107 mL — offered here as an option precisely because it is the error people make. In a ratio, the parts sum to the whole.
Question 5 — military time
A medication is due every 6 hours. The first dose is given at 0730. When is the third dose due?
- A1330
- B1730
- C1930
- D2130
Explanation
The first dose is at 0730, the second at 1330, and the third at 1930. The trap is counting three intervals instead of two — the first dose is not preceded by one. 1330 is the second dose. Military time runs 0000 to 2359 with no AM or PM, so 1930 is half past seven in the evening.
What to drill
- The dosage formula, until setting it up is automatic: (want ÷ have) × volume.
- Conversions in both directions — pounds and kilograms, millilitres and litres, milligrams and grams.
- Ratios where the parts sum to the whole, which is where most ratio marks are lost.
- Fractions, decimals and percentages as three views of the same number.
- Military time, including crossing midnight.
Then sit fifty of them against a clock. Math is the section where untimed practice most flatters your real performance.