Question 661955
The area of the rectangle is
{{{(20cm)(5cm)=100cm^2}}}.
If the side of the square is {{{x}}} cm long, its area, in {{{cm^2}}} is
{{{x^2}}}.
If the area of the square and the rectangle are equal,
{{{x^2=100}}} --> {{{x=10}}} because {{{10^2=100}}} <---> {{{sqrt(100)=10}}}
So the side of the square is {{{10cm}}} long.
The perimeter of the square is four times the length of the side, so it is
{{{4*(10cm)=highlight(40cm)}}}