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# Finding dimensions of a rectangle?

The length of a rectangle is four times it’s width.

If the perimeter of a rectangle is 90cm

What is length and width

Can someone please help me

### 5 Answers

- coverdalerLv 52 years ago
The perimeter of two of the sides, the length and the width, is 45cm.

We can divide this by five (4+1, because four of the width is the same as one of the length), and find the length.

We then multiply the length by 4 to get the width.

Width- 36cm

Length- 9cm.

- lenpol7Lv 72 years ago
P = 2(l + w)

But l = 4w

Substitute

P = 2(4w + w)

P = 2(5w)

P = 10w

90 = 10w

w = 9

Hence

l = 4 x 9 = 36

- vulcan_alexLv 72 years ago
Let x = the width

Then 4x is the length

The perimeter is than 2x + 8x or 10X

10x = 90 cm, so x = 9 cm. You can do the rest, at least I hope you can.

Algebra requires you to show all your work so I have done so.

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- Mr. SmartypantsLv 72 years ago
Let's use w for the width. The length is 4w.

So what is the perimeter of a rectangle? It's two times its width plus two times its length, right? So 2*w+2*4w, which is 2w+8w, which is 10w. So whatever the perimeter of the rectangle is, the width is 1/10 of it and the length is 4/10 of it.