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.

A
0.5
B
0.6
C
0.65
D
None of these

Solution:

Let M and B denote the student of Mathematics and Biology.

Given,

$\begin{array}{l} P (M) = 40 %, P (B) = 30 % \\ P (M \cap B) = 10 % \end{array}$

[10% of the class study both subjects i.e. they ate common in both subjects]

$\begin{array}{l} ∴ P (M or B) = P (M \cup B) \\ = P (M) + P (B) - P (M \cap B) \\ = \frac{40}{100} + \frac{30}{100} - \frac{10}{100} \\ = \frac{60}{100} = 60 % = 0 .6 \end{array}$

Solution:

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