The net of a rectangular prism will have 6 rectangles. To see why, imagine unfolding the rectangular prism so that each face lies flat. There will be two rectangles with dimensions 6 cm x 5 cm (the top and bottom faces), two rectangles with dimensions 4 cm x 5 cm (the side faces), and two rectangles with dimensions 6 cm x 4 cm (the front and back faces). Therefore, there are two rectangles with dimensions 6 cm x 4 cm in the net.
