SIG (Susquehanna)–styleTraderAssistant TraderQuestion #18
Every morning, Mike the security guard at CP High School opens all 1000 doors in the building, numbered 1 to 1000. The next guard closes all even-numbered doors. Each subsequent guard toggles (opens if closed, closes if open) every nth door, where n is the guard's number, until the 1000th guard toggles only door 1000. How many doors are left open in the end?
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 SIG (Susquehanna)–Style Trader Questions
If you roll two dice and add their results, what is the probability of obtaining a sum of 6?You are a player on a basketball team that is losing by 2 points. You have the ball, and there are 3 seconds remaining. You have two options: pass to a teammate for a 3-point shot (with a 37% probability of making it and winning the game), or pass for a 2-point shot (with a 77% probability of making it and tying the game). In the event of a tie, your team goes to overtime, where there is a 50% chance of winning. What should you do, and why?A boat fires torpedoes at another boat. The probability that a torpedo hits is 1/3. If a torpedo hits the boat, the boat is destroyed. Two torpedoes are fired. What is the probability that the ship is destroyed?You have 17 coins and I have 16 coins. We flip all the coins at the same time. If you have more heads than I do, you win; if we have the same number of heads or you have fewer, then I win. What is your probability of winning?You roll a die and win twice the value of the face if it is even, or the face value if it is odd. What is the fair amount to charge to play this game? If you are given the option to roll again and will only be paid based on the result of the second roll if you choose to roll again (i.e., the result of the last roll), what is the fair charge to play the game with this option?
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