Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 2 - Set Theory - 2.5 Survey Problems - Exercise Set 2.5 - Page 103: 28

Answer

The number of elements for the different asked regions is shown below:

Work Step by Step

Simplify region II: \[n\left( A\cap B \right)=6\]is equal to region II\[+\]V. \[\begin{align} & \text{II}+\text{V}=6 \\ & \text{II}+2=6 \\ & \text{II}=4 \end{align}\] For region IV: \[n\left( A\cap C \right)=7\]is equal to region IV\[+\]V. \[\begin{align} & \text{IV}+\text{V}=7 \\ & \text{IV}+2=7 \\ & \text{IV}=5 \end{align}\] For region VI: \[n\left( B\cap C \right)=8\]is equal to region VI\[+\]V. \[\begin{align} & \text{VI}+\text{V}=8 \\ & \text{VI}+2=8 \\ & \text{VI}=6 \end{align}\] For region I: \[n\left( A \right)=21\]is equal to region I\[+\]II\[+\]IV\[+\]V. \[\begin{align} & \text{I}+\text{II}+\text{IV}+\text{V}=21 \\ & 4+2+5+\text{I}=21 \\ & \text{I}=21-11 \\ & \text{I}=10 \end{align}\] For region III: \[n\left( B \right)=15\]is equal to region II\[+\]III\[+\]V\[+\]VI. \[\begin{align} & \text{II}+\text{III}+\text{V}+\text{VI}=15 \\ & 4+2+6+\text{III}=15 \\ & \text{III}=15-12 \\ & \text{III}=3 \end{align}\] For region VII: \[n\left( C \right)=14\]is equal to region IV\[+\]V\[+\]VI\[+\]VII. \[\begin{align} & \text{IV}+\text{V}+\text{VI}+\text{VII}=14 \\ & 5+2+6+\text{VII}=14 \\ & \text{VII}=14-13 \\ & \text{VII}=1 \end{align}\] For region VIII: \[\begin{align} & \text{VIII}=32-n\left( A\cup B\cup C \right) \\ & =32-\left( 10+5+4+3+2+6+1 \right) \\ & =32-31 \\ & =1 \end{align}\]
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