How many cubes with sides 1cm long does it take to make a cube with sides 2cm long?
Solution:
To make a cube with sides 2cm long you need to make a layer of 4 cubes (2x2), which is 1cm high, and then add another 4 cubes on top to make the new cube 2cm high.
The total number of cubes is 2 x 2 x 2, which is 8 cubes.