Since half of the diagonal is [tex]10[/tex] the whole diagonal ([tex]MK[/tex]) is 20
By pythagorean theorem, [tex]JK = \sqrt{MK^2 - MJ^2} = \sqrt{20^2 - 12^2} = \sqrt{400 - 144} = \sqrt{256} = 16. [/tex]
After that you just find the perimeter of the rectangle.
[tex]2l + 2w = 2*16 + 2*12 = 32 + 24 = 56[/tex] :)
