# Writing equations help needed!! Test Tomorrow!!

• Apr 2nd 2009, 05:26 PM
BubblyCuppycake489
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?
• Apr 2nd 2009, 05:48 PM
Mush
Quote:

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.
• Apr 3rd 2009, 03:43 PM
stapel
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. (Wink)