Question

50 students in a class were asked at the beginning of the week what they did at the weekend. 18 read their books, while 28 watched films, and 7 neither read their books nor watched films. How many students both read their books and watched films?​

Answer 1

so 3 people both read their books and watched films.

Explanation:

n(U) = 50

n(A) = 18 ( read books)

n(B) = 28 ( watched films)

n(A U B) with a line at the top = 7

so

Finding n(AUB)

n( A U B) with a line at the top = n(A) + n(B) - n( A n B)

7 = 50-n(A U B)

or, n( A U B) = 50 - 7

so, n(A U B) = 43

Then

n( A U B) = n(A)+n(B)-n(A n B)

43 = 18 + 28 - n( A n B)

or, 43 = 46 - n(A n B)

or, n(A n B) = 46 - 43

so, n(A n B) = 3