### Instruction: The length of a rectangle is three times its width. The perimeter is 160 cm. What is the number of square centimeters in the area of the rectangle?### Response: First let's find the width. Then we can find the length and finally the area.
How do we find the width?
We need to use the formula for the perimeter, which is $2\cdot width + 2\cdot length = 160$.
That makes sense. What do we know?
We know that the length is 3 times the width. So let's call the width x and the length 3x.
So we have $2x + 2\cdot 3x = 160$?
Yes. We just need to solve for x.
$2x + 6x = 160$?
$8x = 160$.
$x = 20$.
So the width is 20 and the length is 3 * 20 = 60.