Question

In Class XI of a school 40% of the student's 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.

Answer 1

Let A be the event in which the selected student studies Mathematics and B be the event in which the selected student studies Biology.

Accordingly,$P(A) = 40$% =$\frac{40}{100}=\frac{2}{5}$

$P(B) = 30$%=$\frac{30}{100}=\frac{3}{10}$

$P(A$ and $B) = 10$%=$\frac{10}{100}=\frac{1}{10}$

We know that $P(A$ or $B) = P(A) + P(B) \- P(A$ and $B)$

$∴P(A$ or B)$$=\frac{2}{5}+\frac{3}{10}-\frac{1}{10}=\frac{6}{10}=0.6
Thus, the probability that the selected student will be studying Mathematics or Biology is 0.6.