Question 21
In a junior carpentry contest, Trung uses wooden cubes to build staircases as shown. A staircase with 2 steps uses 3 cubes; one with 3 steps uses 6 cubes; and the pattern continues. He needs 10 ml of paint for one cube face. How many tins of paint are needed to paint all the faces of a staircase with 10 steps? Each tin contains 500 ml.
