College Algebra (11th Edition)

Published by Pearson
ISBN 10: 0321671791
ISBN 13: 978-0-32167-179-0

Chapter 5 - Section 5.2 - Matrix Solution of Linear Systems - 5.2 Exercises - Page 500: 51

Answer

Wage of a laborer: $\$152$ Wage of a concrete finisher: $\$ 160$

Work Step by Step

Let's note: $x \rightarrow$ the wage of each laborer $y \rightarrow$ the wage of each concrete finisher Here, we have the a set of equations on the basis of given statements as follows: $$ 7x+2y=1384 ~~(1) \\ x+5y =952 ~~~(2)$$ The matrix form for equations (1) and (2) would be as follows: \[ \left[ \begin{array}{cc|c} 7 & 2 & 1384 \\ 1 & 5 & 952 \end{array} \right] \] Next, $R1 \rightarrow -7R2+R1$, we get: \[ \left[ \begin{array}{cc|c} 0 & -33 & -5280 \\ 1 & 5 & 952 \end{array} \right] \] Now, divide $R1$ by $-33$ \[ \left[ \begin{array}{cc|c} 0 & 1 & 160 \\ 1 & 5 & 952 \end{array} \right] \] Next step would be multiply $R1$ by $-5$ and add it to $R2$ \[ \left[ \begin{array}{cc|c} 0 & 1 & 160 \\ 1 & 0 & 152 \end{array} \right] \] Hence, the required answers are: $x= \$152$ and $y =\$ 160$. Thus, wage of laborers; $x= \$152$ and wage of concrete finishers $y =\$ 160$.
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