Question

4. 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 only mathematics not physics​

Answer 1

Answer:

As per data total teachers 20

maths teachers -(m)-10

Physics teasers(p)-9

Who teaches both maths and physics-4

None teaches maths and chemistry

By this we conclude that 6 teachs only maths

So out of 20 teachers 6 teachers are maths and 4 teachs both maths and physics

Rest 10 people teaches physics and chemistry

Since 7 people teach chemistry

And 5 people(phycis teacher's-both maths and physics teachers=9–4) teaches phycics

In 10 people 7 are chemistry and 5 are physics

So that 2 people teaches both physics and chemistry

If we minus above 2 from physics teachers

3 people only teaches physics