Question

pls solve the problem

Answer 1

Diagonal of a square =
$s \sqrt{2}$
where s is the side of the square.

Therefore,
$s \sqrt{2} = 10 \sqrt{2}$
$s = 10cm$
Perimeter=4s=4×10=40cm.

Answer 2

if diagonal is 10√2 then it's sides must be 10 cm
because if we make a diagonal in a square it will form a right isosceles triangle which makes sure that the third side will be a√2 where a is length of common side you can also find it by applying Pythagoras theorem in it .
as far we are confirmed that side is 10 cm the perimeter will be 40 cm for sure because it is 4a .
hope this might help you