Which of the following is both a perfect square and a perfect cube? 64
16
81
1,000

I know the answer is 64, but how? Can someone please explain me to me how to work this out?

Well the square root of 64 is 8, and the cube root of 64 is 4. They’re perfect whole numbers. We know 4 x 4 = 16 is a square from the fact above, and also because of what a square means. But we can go one step further. 4 x 16 = 64 is the product of two squares, so it is also a square. But you can also write it as 64 = 4 x 4 x 4, making it a cube.