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Probability

Question
CBSEENMA12033729

In a hostel, 60% of the students read Hindi newspaper, 40% read English newspaper and 20% read both Hindi and English newspapers. A student is selected at random.
Find the probability that she reads neither Hindi nor English newspaper.

Solution

Let A and B be two events such that
A : a student reads Hindi newspaper
B : a student reads English newspaper.
therefore space space space space space straight P left parenthesis straight A right parenthesis space equals space 60 over 100 space equals 3 over 5 comma space space space space straight P left parenthesis straight B right parenthesis space equals space 40 over 100 space equals space 2 over 5
space space space space space space space space space space space straight P left parenthesis straight A space intersection space straight B right parenthesis space equals space 20 over 100 space equals 1 fifth
 P(student reads neither Hindi nor English newspaper)
      equals space straight P left parenthesis straight A to the power of straight c space and space straight B to the power of straight c right parenthesis space equals space straight P space open square brackets open parentheses straight A space union space straight B close parentheses to the power of straight c close square brackets space equals space 1 space space minus space straight P left parenthesis straight A space union space straight B right parenthesis
space equals space 1 minus open square brackets 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 space intersection space straight B right parenthesis close square brackets
space equals space 1 minus open square brackets 3 over 5 plus 2 over 5 minus 1 fifth close square brackets space equals space 1 minus 4 over 5 space equals space 1 fifth

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