Forty students watched films A, B and C over a week

Q. Forty students watched films A, B and C over a week. Each student watched either only one film or all three. Thirteen students watched film A, sixteen students watched film B and nineteen students watched film C. How many students watched all three films?

            (A) 0                (B) 2                           (C) 4                           (D) 8

Ans: 4

Sol:

Total students=40

13−x+16−x+19−x+x=40

Students watched all three movies
x=4