Multiple choice

T hree unbiased coins are tossed. What is the probability of getting at most two heads?

  1. $\dfrac{3}{4}$
  2. $\dfrac{1}{4}$
  3. $\dfrac{3}{8}$
  4. $\dfrac{7}{8}$
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D Correct answer
Explanation

Total outcomes = 2^3 = 8. Outcomes with at most two heads are all except (H,H,H). There is only 1 outcome with three heads. So, 8 - 1 = 7 favorable outcomes. Probability = 7/8.

AI explanation

When three unbiased coins are tossed, the sample space contains 2^3 = 8 total outcomes. The probability of getting at most two heads can be found using the complementary event, which is getting three heads (HHH). The probability of getting HHH is 1/8, so the probability of getting at most two heads is 1 - 1/8 = 7/8.

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