The number of ducks in a pond is equal to the square root of the number of fish and the number of turtles is equal to the cube root of the the number of fish. The number of fish in the pond is more then 1 but less than 100 . There are no fractional or negative ducks,fish,or turtles. How many fish ducks and turtles are in the pond

d = sqrt f 
t = cuberoot f    (d = ducks, f = fish and t = turtles).

so we need a number f which is a whole number between 1 and 100 and is also a perfect square and a perfect cube.  64 would suit these conditions so we might have

64 fish , 8 ducks and 4 turtles.