If we need to change the average age of a group containing 4 persons from 40 to 38 by adding a person. What should be the age of the person newly added to the group?
Options:
(A) 20
(B) 25
(C) 30
(D) 38
(E) 40 OK. Let's think. Some random thoughts first:
Sum of the ages of the group having 4 persons and average 40 = 4x40 = 160
Sum of the ages of the group having 5 persons and average 38 = 5x38 = 190
Age of the new person added to the group = 190-160 = 30 The answer: (C).