AppliedNumeric answer
A fair coin is flipped 100 times. What is the expected number of positions where flip and flip are both heads?
Answer with a number. Fractions, powers and expressions like 23/6 or C(52,5) are read correctly in practice.
The worked solution is in Premium
The answer, the full working and the one idea to take away – for this and all 1,322 questions in the bank. Answer it in practice and your working is marked, with a known mistake named when you make one.
Learn the method
Reported in interviews at
More probability questions
- You are paid the face value of one roll of a fair six-sided die. What is a fair price?Foundation
- You may re-roll a fair six-sided die as many times as you like, for free, and…Foundation
- What is the expected number of rolls of a fair six-sided die until the first six?Foundation
- A game pays $10 if a fair coin lands heads and nothing otherwise.Foundation
- Let I be 1 when an event A occurs and 0 otherwise. What is 𝔼[I]?Foundation
- You roll a fair six-sided die, then choose whether to re-roll once.Applied