Gujarati
14.Probability
medium

Four persons independently solve a certain problem correctly with probabilities $\frac{1}{2}, \frac{3}{4}, \frac{1}{4}, \frac{1}{8}$. Then the probability that the problem is solved correctly by at least one of them is

A

$\frac{235}{256}$

B

$\frac{21}{256}$

C

$\frac{3}{256}$

D

$\frac{253}{256}$

(IIT-2013)

Solution

$P \text { (problem solved by at least one) }=1- P \text { (problem is not solved by by all) } $

$=1- P (\overline{ A }) P (\overline{ B }) P (\overline{ C }) P (\overline{ D }) $

$=1-\left(\frac{1}{2}\right)\left(\frac{1}{4}\right)\left(\frac{3}{4}\right)\left(\frac{7}{8}\right)=1-\frac{21}{256}=\frac{235}{256}$

Standard 11
Mathematics

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