Question

In a school there are 20 teachers who teach mathematics or physics. Of

these, 12 teach mathematics and 4 teach both physics and mathematics. How many

teach physics ?​

Answer 1

Step-by-step explanation:

Number of teachers who teach math or physics =n(M∪P)=20

Number of teachers who teach math = n(M)=12

Number of teachers who teach math and physics =n(M∩P)=4

so

Number of teachers who teach physics = n(P)

n(M∪P)=n(m)+n(P)−n(M∩P)

20=12+n(P)−4

20−12+4=n(P)

n(P)=12

hence 12 teacher teach the physics

Answer 2

Number of teachers who teach math or physics =n(M∪P)=20

Number of teachers who teach math = n(M)=12

Number of teachers who teach math and physics =n(M∩P)=4

Find : Number of teachers who teach physics =n(P)=?

Solution :

n(M∪P)=n(m)+n(P)−n(M∩P)

20=12+n(P)−4

20−12+4=n(P)

n(P)=12

hence 12 teacher teach the physics!!