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  • In Class XI of a school 40% of the students study Mathematics and 30% study Biology 10% of the class study both Mathematics and Biology If a student is selected at random from the class find the probability that he will be studying Mathematics or Biology.

18.    In Class XI of a school  \small 40\% of the students study Mathematics and \small 30\%  study Biology. \small 10\% of the class study both Mathematics and Biology. If a student is selected at random from the class, find the probability that he will be studying Mathematics or Biology. 

Answers (1)

best_answer

Let M denote the event that the student is studying Mathematics and B denote the event that the student is studying Biology

And total students in the class be 100.

Given, n(M) = 40 \implies P(M) = \frac{40}{100} = \frac{2}{5}

n(B) = 30\implies P(M) = \frac{30}{100} = \frac{3}{10}

n(M \cap B) = 10\implies P(M) = \frac{10}{100} = \frac{1}{10}

We know,

P(A \cup B) = P(A)+ P(B) - P(A \cap B) 

\implies P(M \cup B) = 0.4 + 0.3 - 0.1 = 0.6

Hence, the probability that he will be studying Mathematics or Biology is 0.6 

Posted by

HARSH KANKARIA

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