Question

Five boys go to a store and each buys a notebook, an eraser, and a pen. Find an expression for the total cost (in dollars) if the price of a notebook is $\$x$, an eraser is $\$y$, and a pen is $\$z.$

• A. $x+y+z$
• B. $5x+y+z$
• C. $5x+5y+z$
• D. $5x+5y+5z$

Answer 1

The correct option is D $5x+5y+5z$

$\bullet$ Cost of $1$ notebook $=\$x$
As $5$ boys go to the store and each purchases $1$ notebook, total notebooks purchased $=5$

$\therefore$ Cost of $5$ notebooks
$=5\times$ Cost of $1$ notebook
$=5\times \$x$
$=\$5x$

$\bullet$ Cost of $1$ eraser $=\$y$
As $5$ boys go to the store and each purchases $1$ eraser, total erasers purchased $=5$

$\therefore$ Cost of $5$ erasers
$=5\times$ Cost of $1$ eraser
$=5\times \$y$
$=\$5y$

$\bullet$ Cost of $1$ pen $=\$z$
As $5$ boys go to the store and each purchases $1$ pen, total pens purchased $=5$

$\therefore$ Cost of $5$ pens
$=5\times$ Cost of $1$ pen
$=5\times \$z$
$=\$5z$

Total cost of all the items purchased by $5$ boys would be the sum of the Cost of $5$ notebooks, the Cost of $5$ erasers and the Cost of $5$ pens.

$\therefore$ The total Cost $=\$(5x+5y+5z)$

As a result, $5x+5y+5z$ is the expression for the total cost (in dollars) of the $3$ items purchased by each of the five boys.

Therefore, option (d.) is the correct answer.