Answer the following question, with explanation first.
The length of a rectangle is four times its width. If the area is 100 m2. what is the length of the rectangle?

20
Let L be the length and W be the width of the rectangle.

Hence L = 4 * W.

We now use the area to write 80 = L * W.

Substitute L by 4 W in the equation above 80 = 4 * W × W = 4 W^2.

Solve for W and find L.

4 W^2 = 100.

W^2 = 25, W = 5 and.

L = 4 * 5 = 20 m.

.

The answer is 20