# Thread: Writing equations help needed!! Test Tomorrow!!

1. ## Writing equations help needed!! Test Tomorrow!!

'Kso, I have a math test tomorrow and I just stumbled across this question which I don't get. You have to write an equation for the problem and then solve it. Could I possibly get some help? It's urgent...

The width of a rectangle is one third the length, the perimeter is 48cm. Find the length and width, how would I represent this as an equation and then solve it?

2. Originally Posted by BubblyCuppycake489
'Kso, I have a math test tomorrow and I just stumbled across this question which I don't get. You have to write an equation for the problem and then solve it. Could I possibly get some help? It's urgent...

The width of a rectangle is one third the length, the perimeter is 48cm. Find the length and width, how would I represent this as an equation and then solve it?
If the length of the rectangle is 3 times as long as the width then:

$l = 3w$

You also know the perimeter. The permiter is the length of the outside of the rectable, which is made up of two straight lines the length of the width, and 2 straight lines the length of the length, hence:

$2l+2w = 48$

You now have 2 equations in 2 unknowns, and can solve.

3. If you're not yet familiar with systems of equations, you can just plug the "3w" from the first equation in for the "l" in the second equation:

. . . . . $2(3w)\, +\, 2w\, =\, 48$

Solve for the value of "w", and then back-solve for the length.