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.

# 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.

1. A

0.5

2. B

0.6

3. C

0.65

4. D

None of these

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### Solution:

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

Given,

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

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

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