Well, I have to write 20 words, so... I think this is enough.

Explanation:

Each circle has a radius of 'a'. So r = a.

The area of each circle is pi*r^2 = pi*a^2

The area of each square with side length b is b^2

The two stacks have the same volume only when the circle area is equal to the square area, so whenever pi*a^2 = b^2 is true.

Solving for b leads to b = sqrt(pi*a^2) = sqrt(pi)*a

The stacks must also be the same height for the volumes to be the same, so m = n as well.

25% is the answer

susie has 7 apples