Find the length of the side of the square that has the same area as a circle with radius r cm.

Let's say that the length of the side of the square is a. The area of the square will be length^2 = a^2

Now the area of a circle is given by πr^2. If the area of the square and the circle are equal, we can say that a^2 = πr^2, therefor a = sq.root of (πr^2) = r*sq.root of π (as an exact answer), or 1.772r (to three decimal places)