Question of the day
2026-09-18
Brain Teasers
You flip a fair coin 3 times. What is the probability of getting exactly two heads?
Answer it out loud first — like you would in the room. Then check yourself:
Reveal the model answer
Model answer
3/8.
There are 2³ = 8 equally likely sequences. Exactly two heads: HHT, HTH, THH = 3 ways. So 3/8 = 37.5%.
General form: C(3,2) · (1/2)² · (1/2)¹ = 3 · 1/8 = 3/8. This is the binomial distribution with n = 3, p = 1/2.
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