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

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

Solution

P2+P3…≥0.96
1-P0-P1≥0.96
1-0.96≥nC012n+nC112n
⇒0.042n≥1+n
⇒4.2n≥n+1100
⇒2n+2≥n+1100
As, 210≥900
⇒n=8

Asked in: JEE Advanced 2015 (Paper 1)

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