Engineering
Mathematics
Binomial Probability Theorem
Question

The minimum number of times a fair coin needs to be tossed, so that the probability of getting at least two heads is at least 0.96 is

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Solution

Let minimum number of tosses be n.

  Probability of atleast two heads = 1 – P (no head) – P (exactly one head)

 

(12)nnC1·(12)n1·(12)0.96

⇒ 1 – (n + 1) (12)n 0.96

⇒ (0.04) (n+1)2n

⇒ 2n+2  100 (n + 1)

By hit and trial

Minimum value of n will be 8.