Posted by **Andy** on Wednesday, July 15, 2009 at 11:08pm.

A rectangle has area 6 cm (squared) and diagonal of length 2√5 cm. What is its perimeter?

thanks

- math -
**Reiny**, Thursday, July 16, 2009 at 8:49am
let the width be x and the length be y

we know xy = 6 and

x^2 + y^2 = (2√5)^2 = 20

Perimeter = 2(x+y)

from algebra we know

(x+y)^2 = x^ + 2xy + y^2

but we know the values on the right side,

so

(x+y)^2 = 20 + 6 = 26

then x+y = √26

and the perimeter is 2√26

- math -
**David**, Wednesday, July 29, 2009 at 8:33am
let the width be x and the length be y

we know xy = 6 and

x^2 + y^2 = (2ã5)^2 = 20

Perimeter = 2(x+y)

from algebra we know

(x+y)^2 = x^ + 2xy + y^2

but we know the values on the right side,

so

(x+y)^2 = 20 +12=32

then x+y = ã32

and the perimeter is 2ã32

- math -
**David**, Wednesday, July 29, 2009 at 8:38am
Why is math so hard?

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