The average age of an 8-member committee is the same today as it was 4 years ago, because one old member has since been replaced by a younger one. How many years younger is the new member than the member replaced?

Explanation

1. 01

   In 4 years, the 8 original members would have added $8 \times 4 = 32$ years to the total.

2. 02

   The average is unchanged, so the total is unchanged too.

3. 03

   The replacement must remove exactly those 32 years: the new member is 32 years younger than the one replaced.