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 Q. 5: The probability that a bulb produced by a factory will fuse after 150 days of use is 0.05. Find the probability that, out of 5 such bulbs

              (ii) not more than one will fuse after 150 days of use.

Answers (1)

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Let X represent the number of bulbs that will fuse after  150  days of use.  Trials = 5

           P=0.005

                                                                                                                                                                                                                                                     q=1-0.005=1-0.005=0.95

X has a binomial distribution with n = 5.

\therefore \, \, \, \, P(X=x)=^nC_x.q^{n-x}.p^x

                P(X=x)=^5C_x.(0.95)^{5-x} . (0.05)^{x}

             Put X\leq 1 ,

                   P(X\leq 1)=P(X=0)+P(X=1)

                                          =^5C_0.(0.95)^{5} . (0.05)^{0}+^5C_1 (0.95)^{4} . (0.05)^{1}

                                          =(0.95)^{5}+ (0.25)(0.95)^4

                                          =(0.95)^{4}(0.95+ 0.25)

                                         =(0.95)^{4}\times 1.2

Posted by

seema garhwal

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