the average age of 10 members in a committee is the same as it was 4 years ago, an old member is replaced by a young member. how much younger is the new member

Question

I don't understand

Answer 1

In order for the average age to stay the same 4 years later, the total of the ages has to decrease by 40 (4 years per each member), so the new member is 40 years younger than the member he/she replaced.

 

(25 + 30 + 32 + 35 + 40 + 42 + 43 + 45 + 55 + 65)/10 = 41.2

 

(29 + 29 + 34 + 36 + 39 + 44 + 46 + 47 + 49 + 59)/10 = 41.2

Answer 2

This answer was deleted by Arturo.