# area, perimeter

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the perimeter of rectangle y is equal to its area. rectangle z has the same perimeter as rectangle y. the length of rectangle z is 5 inches and the width is 3 inches. explain how you can find the length and eidth of rectangle y.

• area, perimeter -

perimeter = 2*5+2*3 = 16

2L + 2 W = 16 so L+W=8
WL = 16 so W = 16/L

L + 16/L = 8
L^2 + 16 = 8L
L^2 -8L + 16 = 0
(L-4)(L-4) = 0
L = 4
B = 16/L = 4

• area, perimeter -

from the first description
length ---- x
width ---- y

xy = 2x + 2y
xy - 2y = 2x
y(x-2) = 2x
y = 2x/(x-2)

2nd rectangle is 5 by 3, so its perimeter is 30
so now we know 2x+2y = 30
or x+y = 15
y = 15-x
sub that into the other equation, so
2x/(x-2) = 15-x
2x = 15x - x^2 - 30 + 2x
x^2 -15x + 30 = 0
by the formula
x = 12.623, and subbing back: y = 2.376
or x = 2.376 and subbing back x = 12.623

(notice 2.376 x 12.623 = 29.992 or 30 as expected

• Scrap my answer, go with Damonseter -

I must have have a had a brain-twitch

A 3 by 5 rectangle has a perimeter of 30 ????
Come on Reiny !!!!

• area, perimeter -

i don't get that helppp

• area, perimeter -

No help :(

• area, perimeter -

what is the greatest perimeter of a rectangle wiht an area of 39 square feet

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