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Probability

Question
CBSEENMA12033639

Given that the events A and B are such that P(A) =1 half comma   straight P left parenthesis straight A union straight B right parenthesis space equals space 3 over 5 space and space straight P left parenthesis straight B right parenthesis space equals space straight p. Find p if they are mutually exclusive.

Solution
straight P left parenthesis straight A right parenthesis space equals space 1 half comma space space straight P left parenthesis straight B right parenthesis space equals space straight p comma space space space space straight P left parenthesis straight A union straight B right parenthesis space equals space 3 over 5
Since A and B are mutually exclusive events
therefore space space space space space straight P left parenthesis straight A intersection straight B right parenthesis space equals space 0                         ...(1)
Now,  straight P left parenthesis straight A union straight B right parenthesis space equals space straight P left parenthesis straight A right parenthesis space plus space straight P left parenthesis straight B right parenthesis space minus space straight P left parenthesis straight A intersection straight B right parenthesis

therefore space space space space space space space space space space space 3 over 5 space equals 1 half plus straight p minus 0 space space space space space space space space space space space space space space space space open square brackets because space of space left parenthesis 1 right parenthesis close square brackets
rightwards double arrow space space space space space space space space space space space space space space space straight p space equals space 3 over 5 minus 1 half space equals space fraction numerator 6 minus 5 over denominator 10 end fraction space equals 1 over 10

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