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

20 teachers who teach math(M) ,or Physics(P) = n(M∪P) =20
n(M)=12
n(M∩P) =4
n(P) = ?

n(P) = n(M∪P)+n(M∩P)-n(M)

=20+4-12
=24-12
=12
12 teach physics

Answer 2

Hey !!

Answer:

= 12

Step-by-step explanation:

Let M denote the set of teachers who teach mathematics and P denote the set of teachers who tech physics.

NOTE :- In the statement of the problem, the word "or" gives us a clue of union and the word ''and'' give us a clue of intersection.

Therefore we have n(M ∪ P) = 20 , n(M) = 12 and n(M ∩ P) = 4

      We wish to determine n(P)

Now, Using the result

n(M ∪ P) = n(M) + n(P) - n(M ∩ P)

We obtain,

             20 = 12 + n (P) - 4

Thus,

               n(P) = 12

Hence 12 teachers teach physics.

GOOD LUCK !!