Question

Example 24 In a school there are 20 teachers who teach mathematics or physil

these, 12 teach mathematics and 4 teach both physics and mathematics. How Ex
teach physics ?​

Answer 1

The number of teachers who teach physics n(P) = 12

Explanation:

Step(i):-

Given that the number of teachers who teach mathematics or physics

n(MUP) = 20

Given that the number of teachers who teach mathematics

n(M) = 12

Given that the number of teachers who teach both mathematics and physics

n(M∩P) = 4

Step(ii):-

By using n(A∪B) = n(A) + n(B) - n(A∩B)

n(M∪P) = n(M) +n(P) - n(M∩P)

20 = 12 + n(P) - 4

20 -12 +4 = n(P)

n(P) = 12

Final answer:-

The number of teachers who teach physics n(P) = 12