If half a gallon of paint covers 1/6 of a wall, then we need 6 1/2 gallons of paint. To make this simpler, we can just say that a gallon of paint can cover 2/6 of the wall. This means that with 2 gallons of paint, we can cover 4/6 of the wall. 3 gallons of paint will cover 6/6 of the wall.
