40×30×4+50 40

=4800+2000

=6800 (square centimeter)

2、

40 liters =40 cubic decimeters = 40,000 cubic centimeters.

=40000÷(50×40)

=40000÷ 2000

=20 cm

3、

2.5×50×40

=250×40

=5000 (cubic centimeter)