SOLUTION: The length of a rectangle is five times its width. If the area of the rectangle is 320 cm2 , find its perimeter.

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Question 722993: The length of a rectangle is five times its width.
If the area of the rectangle is 320 cm2 , find its perimeter.
Answer by 119078(26) About Me  (Show Source):
You can put this solution on YOUR website!
So write down what you know and draw the rectangle.
You know that the area is 320cm^2, write that in the middle.
Then l=5w because length is five times greater than width.
The formula for area is A=lw so plug in the numbers you have and plug 5w for length.
You then get 320=(5w)w. You must multiply 5w to w which will give you 5w^2=320. From there you need to divide 5 on both sides. That way you get rid of the 5 on the left and make 320 into 64. Your problem is now w^2=64. To finish this part you need to find the square root of 64 which is 8 and that gives you your width. Now plug 8 for w in 5w and get your length of 40. Using the formula to get your perimeter P=l+l+w+w or P=2(l)+2(w) plug in 40 for length and 8 for width. P=2(40)+2(8). This equals P=80+16 and then P=96. DO NOT FORGET TO LABEL!!!
Here is everything but not so wordy.
l=5w w=? A=320cm^2 P=? A=lw P=2l+2w
320=%285w%29w -> 320=5w%5E2 -> %28320%29%2F%285%29=%285w%5E2%29%2F%285%29 -> root%282%2C64%29=root%282%2Cw%5E2%29 8=w
l=5(8)=40cm w=8cm A=320cm^2 P=? A=lw P=2l+2w
P=2%2840%29%2B2%288%29 -> P=80%2B16 -> P=96
l=40cm w=8cm A=320cm^2 P=96cm
LABEL!