Heads and Tails (Probability)
Probability
Level
2
What is the probability of getting at least 2 heads out of 3 fair coin tosses?
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1 solution
Let's break this down into 2 cases
2 heads: There are 3 options to choose 2 heads, yielding C(3,2)=3. Or you can manually write all the combinations. HHT HTH THH. So the probability of getting 2 heads is 3/(2 2 2)=3/8
3 heads: The only way you can get 3 heads is HHH or C(3,3) or 1. The probability of getting 3 heads is 1/8
The probability of getting at least 2 heads is (1/8)+(3/8)=4/8=1/2