The minimum number of times a fair coin must be tossed so that the probability of getting at least one head exceeds 0.8 is
Question and options
The minimum number of times a fair coin must be tossed so that the probability of getting at least one head exceeds 0.8 is
- 5
- 6
- 3
- 7
Answer and explanation
Correct answer: C - 3
Need 1-(1/2)^n > 0.8, i.e. (1/2)^n < 0.2. n=2 gives 0.25 (no), n=3 gives 0.125 (yes). Minimum 3.
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IPMAT Indore
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