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Probability

Question
CBSEENMA12033708

Kamal and Monica appeared for an interview for two vacancies. The probability of Kamal’s selection is 1 third and that of Monica’s selection is 4 over 5. Find the probability that only one of them will be selected. 

Solution
Let A denote the event ‘Kamal is selected’ and B denote the event ‘Monica is selected’.
therefore space space space straight P left parenthesis straight A right parenthesis space equals space 1 third comma space space straight P left parenthesis straight B right parenthesis space equals space 4 over 5
therefore space space straight P left parenthesis straight A with bar on top right parenthesis space equals space 1 minus straight P left parenthesis straight A right parenthesis space equals space 1 minus 1 third space equals 2 over 3
space space space space space straight P open parentheses straight B with bar on top close parentheses space equals space 1 minus straight P left parenthesis straight B right parenthesis space equals space 1 minus 4 over 5 space equals 1 fifth
P(only one of them is selected)
                         equals space straight P left parenthesis apostrophe straight A space and space straight B with bar on top apostrophe space space space or space space space apostrophe straight A with bar on top space and space straight B apostrophe right parenthesis
space equals straight P left parenthesis straight A space and space straight B with bar on top right parenthesis space plus space straight P left parenthesis straight A with bar on top space and space straight B right parenthesis
space equals space straight P left parenthesis straight A right parenthesis. space straight P left parenthesis straight B with bar on top right parenthesis space plus space straight P left parenthesis straight A with bar on top right parenthesis. space straight P left parenthesis straight B right parenthesis
space equals space 1 third cross times 1 fifth plus 2 over 3 cross times 4 over 5 space equals 1 over 15 plus 8 over 15 space equals 9 over 15 space equals 3 over 5

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