Thinking Mathematically (6th Edition)

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

Chapter 4 - Number Representation and Calculation - Chapter Summary, Review, and Test - Review Exercises - Page 245: 30

Answer

The difference in the indicated base is \[{{345}_{\text{seven}}}\].

Work Step by Step

Start by subtracting the numbers in the right-hand column:\[{{4}_{\text{seven}}}-{{6}_{\text{seven}}}\]. \[{{6}_{\text{seven}}}\]is greater than \[{{4}_{\text{seven}}}\]. So, we need to borrow from the preceding column. Now, borrow one group of 7 because in the provided question we are working in base seven. This gives a sum of \[4+7\] or 11 in base ten. Now, subtract 6 from 11: \[\begin{align} & \text{ 1} \\ & \begin{matrix} \text{ 62}{{\text{4}}_{\text{seven}}} \\ -{{246}_{\text{seven}}} \\ 5 \\ \end{matrix} \\ \end{align}\] Now, subtract the numbers in the second column from the right: \[{{1}_{\text{seven}}}-{{4}_{\text{seven}}}\]. \[{{4}_{\text{seven}}}\]is greater than \[{{1}_{\text{seven}}}\]. So, we need to borrow from the preceding column. Now, borrow one group of 7 because in the provided question we are working in base seven. This gives a sum of \[1+7\] or 8 in base ten. Now, subtract 4 from 8: \[\begin{align} & \text{ 51} \\ & \begin{matrix} \text{ 62}{{\text{4}}_{\text{seven}}} \\ -{{246}_{\text{seven}}} \\ 45 \\ \end{matrix} \\ \end{align}\] Now, perform the subtraction in the third column from the right. \[\begin{align} & \text{ 51} \\ & \begin{matrix} \text{ 62}{{\text{4}}_{\text{seven}}} \\ -{{246}_{\text{seven}}} \\ {{345}_{\text{seven}}} \\ \end{matrix} \\ \end{align}\] The difference in the indicated base is \[{{345}_{\text{seven}}}\].
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