find dimension of rectangle

Question

Find dimension of the rectangle if its length is three times the width and the perimeter is 72 inches.

Answer 1

1. Rectangles have two side lengths--length (l) and width (w). To find the perimeter of a rectangle we just add up the sides: P= l + l + w + w, which we can also write as P=2*l + 2*w
2. We are given the perimeter of 72 inches and told the length is three times the width, i.e. l = 3*w
3. We can therefore substitute our perimeter length of 72 and (3*w) for l in the perimeter equation to solve for w
4. P=2*l + 2*w
5. 72 = 2*(3w) + 2w
6. 72=8w
7. w=9
8. Now that we know the width (9), we can use that to find our length
9. We already know l = 3*w so we can find l by substituting 9 into the equation
10. l = 3*9 = 27
11. Therefore the dimensions of our rectangle are a width of 9 and a length of 27