Quant Screen Speed Practice
This conversation was generated using Cook'd AI's career assistant and reviewed by Fallon Han from our editorial team for accuracy.
I am a third-year physics student at a UK university and I want a high-speed interview that feels like a quant screen. Can you run me through rapid-fire questions on mental math, probability, and short reasoning, then tell me how I did?
Absolutely. I will keep this tight and screen-like.
Round 1: Mental math
1. What is 17 times 6?
2. What is 15 percent of 240?
3. If a price moves from 80 to 92, what is the percentage gain?
Answer all three without overexplaining.
17 times 6 is 102. Fifteen percent of 240 is 36. The move from 80 to 92 is 12 over 80, so 15 percent.
Good start. All three are correct, and the last one is clean.
Round 2: Probability
1. A fair coin is flipped three times. What is the probability of exactly two heads?
2. You draw one card from a standard deck. What is the probability it is a face card or a heart?
3. If two independent events each have a 1 in 5 chance, what is the chance both happen?
Keep your answers short.
Exactly two heads in three flips is 3 over 8. Face card or heart is 12 plus 13 minus 3 over 52, so 22 over 52. Both happening is 1 over 25.
Strong. You handled the overlap correctly on the card question, though say the simplified fraction as 11 over 26. Your probability structure is solid.
Round 3: Rapid reasoning
1. If a strategy wins 54 percent of the time with 1 to 1 payoff, is it profitable in expectation?
2. If you have 10 trades and expect a 0.2 average profit per trade, what is total expected profit?
3. A number is increased by 20 percent and then decreased by 20 percent. Is it back to the original value? Yes or no, then one sentence.
Yes, it is profitable because the win rate is above 50 percent. Total expected profit is 2. No, it is not back to the original value because the decrease is applied to a larger base.
Excellent. You are thinking like a quant screen candidate: concise, correct, and aware of compounding effects.
Evaluation report:
Mental math: 9 out of 10. Fast and accurate.
Probability: 8 out of 10. Good overlap handling, but tighten fraction simplification under pressure.
Rapid reasoning: 9 out of 10. Strong intuition on expectancy and sequential percentage moves.
Overall: 8.7 out of 10.
Best improvement for the next round: practice answering in one sentence first, then add one supporting line only if asked. That will make your responses sound sharper in a prop trading interview.