SOLUTION: The perimeter of a rectangle is 42cm. if the diagonal is 15cm find the width of the rectangle.

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Question 1065330: The perimeter of a rectangle is 42cm. if the diagonal is 15cm find the width of the rectangle.
Answer by math_helper(2461)   (Show Source): You can put this solution on YOUR website!
l,w = length, width, respectively
(1)
(2)
(1) —> —>
Square both sides of (2):

Now substitute "21-w" for "l" in this last expression:


Combine like terms, and rearrange:

Divide through by 2:

Factor:

w = 9 or w = 12
If w = 9, (1) tells us l = 12
if w = 12, (1) tells us l = 9 (<<< discard because convention is l>w for a rectangle)

Ans:
,

Check:
Diagonal = (ok)
Perimeter = (ok)

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