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A die is thrown 7 times. What is the chance thatan odd number turns up(i)exactly 4times(ii)at least 4times |
Answer» Probability of success is 3/6=1/2. `thereforep=1/2andq=1/2` (i) For exactly 4 successes, the required probability is `""^(7)C_(4)((1)/(2))^(4)((1)/(2))^(3)=35/128` (ii) For at least 4 successes, the required probability is `""^(7)C_(4)((1)/(4))^(4)((1)/(2))^(3)+""^(7)C_(5)((1)/(2))^(5)((1)/(2))^(2)` `+""^(7)C_(6)((1)/(2))^(6)((1)/(2))^(1)+""^(7)C_(7)((1)/(2))^(7)` `=35/128+21/128+7/128+1/128=64/128=1/2` |
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