Jane Street–styleQuant ResearcherQuantitative ResearcherQuestion #374
a) Flip 4 coins and you get paid $1 for every head. What is the expected value of your earnings? b) If you have a magic wand that allows you to tap on every pair of coins with opposite faces (one head and one tail) to flip both of them again, what is the expected value of your earnings after using the wand?
Build Your Approach
State the assumptions, try a simple case, then work toward a general solution. Check the result and explain how it changes if an assumption changes.
Try the free diagnostic with worked solutions →Get Free Interview Prep Resources
More Jane Street–Style Quant Researcher Questions
In a Rock-Paper-Scissors game where your opponent is not allowed to play rock, you win $1 for each win, lose $1 for each loss, and draw $0 for a tie. What should you play to maximize your expected profit?You are rolling a die. Each time you roll, you can either stop the game and receive payment equal to the face-up value, or choose to roll again. You may roll up to three times in total. What is the expected gain from playing this game optimally?Suppose you are playing Russian roulette. What is the probability that the person who fires first wins?Given the probabilities with which your opponent will play Rock, Paper, and Scissors, how should you respond to maximize your expected winnings?You have 3,000 apples in Edinburgh and want to transfer as many as possible to London. You have a truck with a maximum capacity of 1,000 apples. London is 1,000 miles away from Edinburgh. For every mile the truck drives while carrying apples, it consumes (or drops) one apple. What is the maximum number of apples you can deliver to London?
Practice the Reasoning Behind the Answer
Bring your target roles and interview timeline to a free quant consult. Discuss your preparation priorities and how Quant Blueprint’s lessons, practice and mock interviews can help.
Book a Free Quant ConsultYour goals · your preparation · your next steps