// QUANT INTERVIEW PREP
Mental Math Quant Interview Prep & Practice
Timed arithmetic is the first filter at most trading firms: eighty questions in eight minutes, no calculator, a penalty for wrong answers on some screens. The questions below are drawn from the generators behind our mock screens.
Sample Mental Math Questions
Question 1 · SIG Quantitative Evaluation
Which of these is the largest?
- 7/15
- 9/20
- 4/9
- 5/12
Question 2 · SIG Equity Research
A deposit quotes a nominal 5.00% a year compounded monthly. What is the effective annual rate?
- 5.0000%
- 79.5856%
- 0.4167%
- 5.1162%
- 5.1271%
Question 3 · Akuna Math and Sequences
Split 243 in the ratio 5:4. Give the larger share.
See the solution ↓Question 4 · Flow Traders Trading Assessment
Average of 72, 85, 74, 81
See the solution ↓Question 5 · Old Mission Quant Screen
How many digits does 2^57 have?
- 18
- 20
- 57
- 29
Step-by-Step Solutions
Solution 1
Which of these is the largest?
Answer: 7/15
As decimals: 9/20 = 0.45, 4/9 = 0.4444, 7/15 = 0.4667, 5/12 = 0.4167. The largest is 7/15.
Solution 2
A deposit quotes a nominal 5.00% a year compounded monthly. What is the effective annual rate?
Answer: 5.1162%
The periodic rate is 5.00% / 12 = 0.4167%, and 12 of those compound into 1 + EAR = (1 + 0.004167)^12 = 1.051162, so EAR = 5.1162%. The nominal 5.00% ignores compounding altogether. Raising the whole annual rate to the power 12 gives 79.5856%, which compounds 12 years rather than 12 periods. Continuous compounding would give 5.1271%, the ceiling this converges to as the periods get shorter.
Solution 3
Split 243 in the ratio 5:4. Give the larger share.
Answer: 135
9 parts, so one part is 243 ÷ 9 = 27. The larger share is 5 × 27 = 135.
Solution 4
Average of 72, 85, 74, 81
Answer: 78
They all sit near 78. The offsets from 78 are -6, 7, -4, 3, which cancel, so the mean is 78. Total 312 ÷ 4 = 78.
Solution 5
How many digits does 2^57 have?
Answer: 18
log10(2) ≈ 0.301, so log10(2^57) ≈ 57 × 0.301 = 17.16. The digit count is one more than the whole part: 18.
How to Pass the Mental Math Screen
Speed comes from recognising the shortcut, not from multiplying faster. Numbers that straddle a round number are a difference of squares, a percentage can be swapped (15% of 240 is 240% of 15), and a division by a decimal clears once you scale both sides.
Skip early. On a screen with negative marking, a question you cannot see a route through in three seconds costs more than it can earn. Come back to it if the clock allows.
Train under the real clock. Untimed practice builds accuracy, but the screen tests accuracy at pace, and the two only meet when you drill with a timer running.
Practice mental math alongside 4,000+ more procedurally generated scenarios under live timer conditions. Unlock Outcry Pro.
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