# 97

Derivatives Trader interview questions shared by candidates

## Top Interview Questions

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### If A and B are playing tennis and the score is 30-30, what is the chance that A wins the game? Assume on any given point, A has a 0.7 chance of winning the point (and B 0.3)

The way I approached it was as follows: Starting from the initial state, one player has to win 2 points in a row to win. If that does not happen, we're back to the initial state. Therefore, P(A) = 0.49, P(B) = 0.09, P(repeating) = 1 - P(A) - P(B) = 0.42 I enjoy using the intuition that A is 49/9 more likely to win and then find the probabilities by dividing both by 0.42 (making 49 and 9 add up to 100 while preserving their proportions). Grats on the JS offer! Less

Shouldn't it be 0.7?

84.5 % (sum of 0.49x(0.42)^n)

### Given two die, what is the probability that the sum when rolled would add up to six?

5/36

5/36 is right.... Combinations that add up to six: 1 and 5, 2 and 4, 3 and 3, 4 and 2, 5 and 1. So we have 5 successes. There are 36 individual outcomes because there are 6 sides on each die and 6*6 = 36 So we have 5/36. Less

1/6

### 3/?=?/48

12

Actually, +/- 12

Hey, could you please tell me more about the final round interview at their office? Less

### 100 pennies in a jar. 1 penny has 'heads' on both sides. You pick a penny out of the jar and give it to your friend (without looking at the penny). Your friend flips the penny in the air and gets 7 heads in a row. Which penny do you have? Why?

Chance of 1 Heads = .5 Chance of 7 heads in a row = (.5)^7 to do this in your head think of fractions... (1/2)^7 = (1/2*1/2=1/4, * 1/2=1/8, * 1/2 = 1/16....if you do it seven times you get 1/128. so you have a better chance to pick out the penny with two heads (1/100) than to get 7 heads in a row (1/128) Less

99 times out of 100 you take the normal penny. prob that normal penny give 7 heads in a row is 1/128. so, prob that he has special penny is 1/100 / (1/100 + 0.99*1/128) = 56.2% Less

~56.4% that you have the 2-headed penny.

### If the current market is in contango and you are short are you losing money or making money?

You’re making a profit. Selling at a higher price than what you bought

The simple answer is that if you are short on a contango curve then you are losing money, for the curve is sloped positively. Less

### You're a casino introducing a new game. The games rules: Playing cards numbered 1 through 10 lay face down on a table, the customer picks a card and whatever number it is he/she wins that dollar value. Ex. I flip a 2 over, I win 2 dollars. Question: How much do we charge for the game? Why?

1+2+3+4+5+6+7+8+9+10=55 55/10 = 5.5 = Average Expected Winning Price it higher then that number to be profitable Less

Whatever will maximize the value from your customers.

### Which sports do you follow? Give me the current standing of the teams in the league/tournament?

Football EPL/ Top 5 current standing are Manchester city, Manchester United, Tottenham Hotspur, Chelsea, watford Less

Cricket. Current standing are Australia, india,sa,nz,sl,eng,pak,wi,ban,zmw

I told them my details