# 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

**Solution:**

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%

= 40/100

= 2/5

P (B) = 30%

= 30/100

= 3/10

P (A and B) = 10%

= 10/100

= 1/10

By addition theorem of probability,

P (A or B) = P (A) + P (B) - P (A and B)

= 2/5 + 3/10 - 1/10

= (4 + 3 - 1)/10

= 6/10

= 0.6

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

NCERT Solutions Class 11 Maths Chapter 16 Exercise 16.3 Question 18

## 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

**Summary:**

The probability that a selected student will be studying Mathematics or Biology is 0.6