Quantitative Trader Interview Questions

1,130 quantitative trader interview questions shared by candidates

You have 100 light bulbs, labeled from 1 to 100. Initially, all of them are off. You perform 100 rounds of toggling: On round 1, toggle every bulb (they all turn on). On round 2, toggle every 2nd bulb (bulbs 2, 4, 6, …). On round 3, toggle every 3rd bulb (bulbs 3, 6, 9, …). ... On round 100, toggle bulb 100. Toggling a bulb means: if it's on, turn it off; if it's off, turn it on. Question: After all 100 rounds, which bulbs are on?
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Quantitative Trader

Interviewed at Jane Street

4.4
Jul 19, 2025

You have 100 light bulbs, labeled from 1 to 100. Initially, all of them are off. You perform 100 rounds of toggling: On round 1, toggle every bulb (they all turn on). On round 2, toggle every 2nd bulb (bulbs 2, 4, 6, …). On round 3, toggle every 3rd bulb (bulbs 3, 6, 9, …). ... On round 100, toggle bulb 100. Toggling a bulb means: if it's on, turn it off; if it's off, turn it on. Question: After all 100 rounds, which bulbs are on?

I sample p uniformly from [0,1] and flip a coin 100 times. The coin lands heads with probability p in each flip. Before each flip, you are allowed to guess which side it will land on. For each correct guess, you gain 1$, for each incorrect guess you lose 1$. What would your strategy be and would you pay 20$ to play this game?
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Quantitative Trader Intern

Interviewed at Jane Street

4.4
Mar 8, 2025

I sample p uniformly from [0,1] and flip a coin 100 times. The coin lands heads with probability p in each flip. Before each flip, you are allowed to guess which side it will land on. For each correct guess, you gain 1$, for each incorrect guess you lose 1$. What would your strategy be and would you pay 20$ to play this game?

Three games, you need to decide which one to play: 1) Throw a normal dice and take the square of the resulting value 2) Throw two dice and take the product of the results 3) Throw 5 dice and take the square of the mode.
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Quantitative Trader

Interviewed at Jane Street

4.4
Mar 13, 2025

Three games, you need to decide which one to play: 1) Throw a normal dice and take the square of the resulting value 2) Throw two dice and take the product of the results 3) Throw 5 dice and take the square of the mode.

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