Questions / Quant trading, Expected value & odds
Sum through a stopping roll
Roll a fair six-sided die until the first 6. Sum all face values, including the final 6. What is the expected sum?
Answer it in the app It's free. You get hints, a second try if you miss, and a follow-up question.
Show the answer and worked solution
Answer: 21 points
- Let E be the expected remaining sum. E = 3.5 + (5/6)E, because a non-6 restarts the remaining problem, so E = 21.
Interview shortcut. Wald: 6 rolls on average × 3.5 per roll.
In the app this has a follow-up where one thing about the setup changes. Try the follow-up.