question_answer

In a school there are 30 teachers who teach Mathematics or Physics. Of these teachers, 20 teach Mathematics and 15 teach Physics, 5 teach both Mathematics and Physics. The number of teachers reaching only Mathematics is

A)  5                                

B)  10

C)  15

D)  20

Correct Answer: C

Solution :

Given that, Number of teachers teach Mathematics, \[a+c=20\]                                ...(i) Number of teachers teach Physics, \[b+c=15\] and number of teachers teach both (M and P) C = 5, From Eq. (i), \[a+5=20\]\[\Rightarrow \]\[a=15\] So, only 15 teachers teaching only Mathematics.