Correct Answer - Option 3 : 51
Given: The average weight of a group of 14 members increases by 1.4 kg when a member weighing 72 kg joins the group.
Formula: Average of n numbers a1, a2, ... an = (a1 + a2 + ... + an)/n
Calculation: Let the average weight of 14 members be x
⇒ (14x + 72)/15 = x + 1.4
⇒ 14x + 72 = 15x + 21
⇒ 51 = x
So, the average weight is 51