Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 13 - Counting and Probability - 13.1 Counting - 13.1 Asses Your Understanding - Page 847: 28



Work Step by Step

Here $A$ is the set attending to the session I and $B$ is the set attending to the session II. According to the counting formula we know that $n(A\cup B)=n(A)+n(B)-n(A\cap B).$ Hence here $n(A\cup B)=n(A)+n(B)-n(A\cap B)=15+20-10=25.$ Hence: $n(A\cup B)=200+150-75=275.$ We know that $275$ students attend neither of the lectures, hence in total there are $275+275=550$ students participated.
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