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A coin is tossed n times. The probability of getting head at least once is greater than `0.8.` Then the least value of n isA. 7B. 6C. 5D. 3 |
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Answer» Correct Answer - D Suppose the coin is tossed n times. Let X be the number of heads obtained. Then, X follows a binomial distribution with parameters n and `p=1//2`. Now, `P(Xge1)ge0.8` `rArr 1-P(X=0)ge0.8` `rArr 1-.^nC_(0)p^0(1-p)^nge 0.8` `rArr ((1)/(2))^nle 0.2rArr ((1)/(2))^nle (1)/(5)rArr 2^nge 5rArr nge 3` Hence, the least value of n is 3. |
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