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:

$10\sqrt{3}m$ $10\sqrt{2}m$ $10\sqrt{7}m$ $10\sqrt{5}m$

$10\sqrt{5}m$

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