Chapter 3.1, Problem 9CYU

(a)

To determine

To Write: the equation that represent cost of printing digital photo of each lab.

Answer to Problem 9CYU

  $y=0.15x+2.70$ and $y=0.25x$

Explanation of Solution

Given:

information are given in the table below.

  $\begin{array}{c}\text{Digital Photos}\\ \begin{array}{l}\text{ Online Store}\\ \$\text{0}\text{.15 per photo+}\$2.70\text{shipping}\end{array}\\ \begin{array}{l}\text{Local Store}\\ \$0.25\text{per photo}\end{array}\end{array}$

Calculation:

Let $y$ be the total cost of printing and $x$ be the number of photos.

Equation for total cost for online store.

  $y=0.15x+2.70$ …… (1)

Equation for total cost for local store.

  $y=0.25x$ …… (2)

Therefore, the equation for online store is $y=0.15x+2.70$ and for local store is $y=0.25x$ .

(b)

To determine

To Find; the condition at which printing cost is same for both labs.

Answer to Problem 9CYU

  $27$ photo for $\$$$6.75$

Explanation of Solution

Given; The equation for online store is $y=0.15x+2.70$ and for local store is $y=0.25x$ .

Here, $y$ is the total cost of printing and $x$ is the number of photos.

Calculation;

Substitute $y=0.25x$ in equation $y=0.15x+2.70$ .

  $\begin{array}{l}y=0.15x+2.70\\ 0.25x=0.15x+2.70\\ 0.25x-0.15x=2.7\\ 0.10x=2.7\\ x=27\end{array}$

Substituting $x=27$ inequation $y=0.25x$ .

  $\begin{array}{l}y=0.25x\\ y=0.25\times 27\\ y=6.75\end{array}$

Therefore, condition is to print $27$ at the cost of $\$$$6.75$ .

So, the answer is $27$ photo for $\$$$6.75$

(c)

To determine

To Find; when it is best to use the online store and when is it best to use local store.

Explanation of Solution

Given; Cost of printing in both is same when you print $27$ photo at the cost of $\$$ $6.75$ .

Explanation; It would be advised to use online store when more than $27$ photos are to be printed and local store if less than $27$ photos.