Two jugs hold 20 litres and 8 litres. What is the range of these two amounts?

Explication

The larger amount is 20 litres and the smaller is 8 litres, so the range is 20 - 8 = 12 litres. Answering 28 litres adds the two amounts, which gives the combined volume and grows as the amounts grow, whereas a range shrinks as two amounts move closer together.