If two squares X and Y have each side of 10 m and 20 m respectively, then the side of the square Z whose area is equal to the sum of the areas of square X and square Y is:

$10\sqrt{5}m$

Two squares X and Y have each side of 10 m and 20 m

Area of X = 100 sqm.

Area of Y = 400 sqm.

Sum of area = 500 sqm

Area of Z = 500 sqm.

Side of Z = sqrt(500) = $10\sqrt{5}m$

The correct answer is Option (4) → $10\sqrt{5}m$