The average weight of the first thirteen persons among fourteen persons is 78 kg. The weight of the 14th person is 39 kg more than the average weight of all the fourteen persons. Find the weight of the 14th person.

Correct option is D

Given:

Average weight of the first thirteen persons among fourteen persons = 78kg

The weight of the 14th person = 39kg + average weight of all the fourteen persons

Concept and Formula Used:

Average: The average of a group of numbers is the sum of the numbers divided by the number of elements in the group.

Algebraic Equations: Formulating and solving equations based on the given conditions.

Solution:

Let average of all 14 persons = x

ATQ,

Weight of 14^th person = x + 39

Now,

14x = 13×78+x+39

​$$\frac {13×78+x+39}{14}=x$$​​

13x = 1053

x = 81

weight of 14^th person = x + 39

= 120 kg