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Probability

Question
CBSEENMA12033723

The probabilities of A, B, C solving a problem are  1 third comma space 2 over 7 space and space 3 over 8 respectively. If all the three try to solve the problem simultaneously find the probability that exactly one of them will solve it.

Solution
Let E, F, G be the events that A, B, C solve the problem.
    therefore space space space straight P left parenthesis straight E right parenthesis space equals space 1 third comma space space straight P left parenthesis straight F right parenthesis space equals 2 over 7 comma space space straight P left parenthesis straight G right parenthesis space equals 3 over 8                straight P left parenthesis straight E with bar on top right parenthesis space equals space 1 minus straight P left parenthesis straight E right parenthesis space equals space 1 minus 1 third space equals space 2 over 3 comma space space straight P left parenthesis straight F with bar on top right parenthesis space equals space 1 minus 2 over 7 space equals 5 over 7 comma space space straight P left parenthesis straight G with bar on top right parenthesis space equals space 1 minus 3 over 8 space equals 5 over 8
P(exactly one solves the problem).
                             equals space straight P left parenthesis straight E space straight F with bar on top space straight G with bar on top space space or space space straight E with bar on top space straight F space straight G with bar on top space space or space straight E with bar on top space straight F with bar on top space straight G right parenthesis
space equals space straight P left parenthesis straight E space straight F with bar on top space straight G with bar on top right parenthesis space plus space straight P left parenthesis straight E with bar on top space straight F space straight G with bar on top right parenthesis space plus space straight P left parenthesis straight E with bar on top space straight F with bar on top space straight G right parenthesis
equals space straight P left parenthesis straight E right parenthesis space straight P left parenthesis straight F with bar on top right parenthesis space straight P left parenthesis straight G with bar on top right parenthesis space plus space straight P left parenthesis straight E with bar on top right parenthesis thin space straight P left parenthesis straight F right parenthesis space straight P left parenthesis straight G with bar on top right parenthesis space plus space straight P left parenthesis straight E with bar on top right parenthesis space straight P left parenthesis straight F with bar on top right parenthesis thin space straight P left parenthesis straight G right parenthesis
space equals space 1 third cross times 5 over 7 cross times 5 over 8 plus 2 over 3 cross times 2 over 7 cross times 5 over 8 plus 2 over 3 cross times 5 over 7 cross times 3 over 8 space equals 25 over 168 plus 20 over 168 plus 30 over 168 space equals 75 over 168 space equals 25 over 26

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