What is the missing length of a square if the area is area=225 cm2?

The formula for the area of a square is A = s^2, where s is the side length. Here, 225 cm^2 = s^2.

To find the side length, we need only take the sqrt of both sides of this equation and eliminate the negative root:

plus or minus √{225 cm^2) = s. Thus, s = 15 cm = side length.