Question

Mrs. Beyer is painting a mural on her rectangular classroom wall. The wall is 10 feet long and 9 feet wide. The mural will be 9 feet long and 8 feet wide. How many square feet of the wall will not be covered by the mural?

Answer 1

$18ft^2$

1) Let's sketch out the wall and the mural to better grasp it:

2) Notice that the wall and the mural have rectangular forms. So we can make use of the formula for the Area of a rectangle. Let's find how many feet in the wall:

$\begin{gathered} A_w=w\cdot l=9\cdot10=90ft^2 \\ A_m=w\cdot l=9\cdot8=72ft^2 \end{gathered}$

3) To find the area that is not covered by the mural we have to perform a subtraction:

$A_U=90-72=18ft^2$

And that is the answer