From the 220 graduating students in a school, 110 attended semi - formal....

Question

From the 220 graduating students in a school, 110 attended semi - formal and 150 attended the prom. If 58 students attended both events, how many students did not attend any event ?

Is this the answer?

We know that,

n(total) = 220

n(semi-formal) = 110

n(formal) = 150

n(both) = 58

110 - 58 = 52 (52 ONLY in semi-formal)

150 - 58 = 92 (92 ONLY in formal)

So then, 220 - 92 - 52 - 58 = 18

Answer 1

You are correct.

There is a simple mathematical reason why your answer is correct, but Wyzant told me that adding it to this answer required review by Wyzant.

Try again:

P(A or B) = P(A) + P(B) - P(A and B)

P(Neither A nor B) = 1 - P(A or B)