Koi Pond Puzzle Answer

Start by assuming the area of the big square is 4 square units instead of acres – it will make the calculations easier. Therefore the sides are 2 units x 2 units.

With a rotation, you can see that the diagonal of the pond and the diameter of the circle are both 2 units.

By Pythagoras, this isosceles right triangle with hypotenuse = 2 has legs √2/2. Thus the area of the smaller square is √2/2 * √2/2 = 2 units² = 2 acres.

SO the pond is 2 acres, or 87120 ft².
(1 acre = 43560 ft²)

Volume = 87120 ft² * 3ft = 261360 ft³
* 7.48051948 gals/ft³ = 1,955,109 gallons