CA Foundation · Quantitative Aptitude · Probability
A fair coin is tossed three times. What is the probability of getting at least two heads?
The probability is 1/2. Three tosses give 8 equally likely outcomes. Exactly two heads occurs in 3 outcomes and three heads in 1 outcome, so 4 outcomes are favourable, and 4/8 equals 1/2.
- A3/8
- B1/2Correct
- C5/8
- D7/8
Explanation
The sample space has 8 outcomes. Exactly two heads can occur in 3 ways and three heads in 1 way, giving 4 favourable outcomes. Probability = 4/8 = 1/2. The value 3/8 counts only exactly two heads and ignores HHH.
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