It is question number 10. use pythagorean theorem.

Hello from MrBillDoesMath!

31.96  (approximately)

Discussion:

Suppose the square has side length "x". Then from Pythagoras,

x^2 + x^2 =  (11.3)^2   =>        (where 11.3 is the length of the hypotenuse)

2x^2 =   127.69           =>       (divide both sides by 2)

x^2 =  127.69/2           =>

x^2 =   63.845            =>       (take the square root of each side)

x = 7.99

Perimeter of the square = 4x

= 4(7.99) =  31.96

Thank you,

MrB