If a board 4 ft.X 8 ft. was cut into 50 pieces, what size would each piece be?

The mathematical answer would be

4*8/50=0.64 sq.ft each

One practical answer, if it is required to have each piece equal, would be to have each piece 0.8ft * 0.8 ft, so there will be 10 rows by 5 columns which fit exactly in a 4x8.