Make an assumption about what the length of the side of the square is if its area is 400 cm2. Perform the calculation.

It is known that the sides of a square are equal, and its area is equal to the square of the side.

Let the side of the square be x cm. Then the area of the square can be expressed as x * x, or x².

Knowing that the area of a square is 400 cm², we compose and solve the equation:

x² = 400;

x = √400;

x = 20.

Check: 20 * 20 = 400 – true

Answer: the side of the square is 20 cm.