SOLUTION: The length of a rectangle is 5 more than twice the width. The perimeter is 130. What is the area? Answer in back of book is that area is 900 sq. units. My son doesn't know how

Algebra ->  Rectangles -> SOLUTION: The length of a rectangle is 5 more than twice the width. The perimeter is 130. What is the area? Answer in back of book is that area is 900 sq. units. My son doesn't know how       Log On


   

Question 295348: The length of a rectangle is 5 more than twice the width. The perimeter is 130. What is the area? Answer in back of book is that area is 900 sq. units. My son doesn't know how to show this.
Found 2 solutions by scott8148, richwmiller:
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
if x is the width, then 2x+5 is the length

p = 2(x) + 2(2x+5)

130 = 6x + 10 ___ x = 20

2x + 5 = 45

a = 20 * 45 = 900

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
You need to know two formulas to do this problem successfully.
Perimeter of a rectangle and area of a rectangle
P=2*(L+W)
A=L*W
We are told that L=2W+5 and that P=130
So we plug that into the formula for perimeter.
130=2*(2W+5+W)
65=3w+5
60=3W
20=W
L=2W+5
L=2*(20)+5
L=45
W=20
A=L*W
A=20*45
A=900
Funny that you mention that your son doesn't know how to show this. What about you,son?