2. The sum of the ages of three children, Ava, Bob and Carlo, is 31 . What will the sum of their ages be in three years' time?
A 34
B 37
С 39
D 40
E 43
Solution
D

In three years' time, each child will be three years older. Hence the sum of their ages will be nine years more than it is at present. Therefore, in three years' time, the sum of their ages will be $31+9=40$.