Class 11

Math

Algebra

Probability

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.

Accordingly $P(A)=40$% $=10040 =52 $

$P(B)=30$% $=10030 =103 $

$P(AorB)=10$% $=10010 =101 $

We know that $P(AorB)=P(A)+P(B)−P(A$ and $B)$

$∴P(AorB)=52 +103 −101 =106 =0.6$

Thus the probability that the selected student will be studying Mathematics or Biology is $0.6$