# Perimeter help: The perimeter of a rectanle is 40cm

#### stahl7639

##### New member
I have a problem that I am stuck on from myhomework assignment.

The perimeter of a rectanle is 40cm. The width is 8cm less than the length. Find the width and the length.

The answer I got from guessing is Length 14 Width 6. Can someone help me use the formula to get the rightanswer to this

2L+2W=40

#### skeeter

##### Senior Member
2L + 2W = 40

The width is 8cm less than the length
W = L - 8

substitute (L - 8) for W in the first equation ...

2L + 2(L - 8) = 40
2L + 2L - 16 = 40
4L - 16 = 40
4L = 56
L = 14

since W = L - 8 ... W = 14 - 8 = 6

#### stahl7639

##### New member
I was going by this to figure out my answer:

2L+2W= 40

L+L+(L-8)(L-8)=40
4L-16=56
56/4= 14
14-8 = 6
Length- 14
Width- 6

Thank you for posting. I wanted to make sure what I was doing was right.

#### Denis

##### Senior Member
stahl7639 said:
I was going by this to figure out my answer:
2L+2W= 40
L+L+(L-8)(L-8)=40
4L-16=56
56/4= 14
14-8 = 6
Length- 14
Width- 6
That's messy, meaning a teacher could deduct marks...
Look at what Sir Skeeter did, and make sure you use that style in the future...