CA Foundation · Quantitative Aptitude · Probability
A fair coin is tossed three times. How many outcomes does the sample space contain, and what is the probability of getting exactly two heads?
Three tosses of a fair coin give 2 x 2 x 2 = 8 equally likely outcomes. Exactly two heads can occur in three ways (HHT, HTH, THH), so the probability is 3/8.
- A8 outcomes; probability 3/8Correct
- B6 outcomes; probability 1/2
- C8 outcomes; probability 1/4
- D6 outcomes; probability 3/8
Explanation
Each toss has 2 results, so the sample space has 2^3 = 8 outcomes. Exactly two heads occurs in HHT, HTH, THH, which is 3 outcomes, so the probability is 3/8. Option with 1/4 counts only 2 favourable outcomes, which is wrong.
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