Question

What is the probability that she would get heads two of the times?

Answer 1

There are 8 possibilities: HHH, HHT, HTH, HTT, THH, THT, TTH, TTT. Of these 4 have at least two heads. Assuming a fair coin, the probability of tossing at least two heads is 4/8 or 1/2. The Answer would probably be 3/8 though.

Answer 2

C) 3/8

Explanation:

The probability of heads is 1/2, so the probability of not-heads is 1/2.

Then the probability of 2 heads and a tails is (1/2)²·(1/2) = 1/8.

There are 3 choose 2 = (3·2)/(2·1) = 3 ways that the pair of heads may appear among the three tosses. Thus the probability of 2 heads in 3 tosses is ...

... 3·(1/8) = 3/8

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Or you can simply count the favorable outcomes among the possible outcomes:

TTT TTH THT THH HTT HTH HHT HHH . . . . 3 of 8 are favorable.