Jane Street interview questions

11% of 68 1,000,000-211 32 x 28 1 bowling ball has diameter of 8 inches, weighs 16 pounds. A bowling ball of equal density has diameter of 12. How much does it weight? We're going to play a game. You go first. You flip a coin and if you get H, I give you $30. If you get T, you give me the coin and I flip. If I get H, you give me $30, if I get T I give it back to you. We keep going until one of us gets heads. What is the max amount you'd be willing to pay to go first. Give a 50% confidence range and a 90% one of your answer. Why?

Given an unfair coin that is heads 2/3 of the time and tails 1/3 of the time, how do simulate a fair coin?