Celano printing recently charged $.49 per page for color copies and nine cents per page for black-and-white copies. If Michaela’s bill for 90 copies was $12.90 how many copies of each type were made?

1 Answer
Feb 26, 2018

12 color copies and 78 black-and-white copies.

Explanation:

Let x=number of color copies and y=number of black-and-white copies. Now set up a system of equations.

0.49x+0.09y=12.90rarrequation 1
x+y=90rarrequation 2

Now, solve. I used substitution below.
equation 2
x=90-yrarrplug into equation 1
equation 1
0.49(90-y)+0.09y=12.90rarrdistribute
44.10-0.49y+0.09y=12.90rarrisolate y terms
-0.40y=-31.20rarrcompletely isolate y
y=78rarrplug into equation 2
equation 2
x=90-78
x=12

So, there were 12 color copies and 78 black-and-white copies.