What is the least number of square pieces into which a cardboard, 13ft long and 8ft wide can be cut?

solution pls...

If you have to cover the whole board, then you will get

8x8 5x5 3x3 2x2 1x1 1x1

It works out nicely because the dimensions are Fibonacci numbers:
1,1,2,3,5,8,13,...