A square piece of paper is folded in half vertically. The resulting figure has a perimeter of 21 in. What is the number of units in the greatest possible perimeter?

Perimeter is adding all 4 sides together.

To find the length and width divide total perimeter by 2:

21 / 2 = 10.5

We now know the length of 1 side and the width of 1 side need to equal 10.5.

Since the original piece was a square we also know the width needs to equal 1/2 of the length.

So we have L + 1/2L = 10.5

Add the common terms 1 L + 1/2 L = 1 and 1/2 L

To Find L divide 10.5 by 1-1/2, which equals 7

To find the width subtract 7 from 10.5, which equals 3.5

So the paper is now 3.5 inches by 7 inches.