The average salary of a group of 12 employees in an institution is Rs. 3,950 per month and that of another group of employees is Rs. 1,850. If the average salary of all employees is Rs. 2,150, then the total number of employees is:

Correct option is C

Given:
The average salary of a group of 12 employees=Rs3950
The average salary of another group of employees=Rs1850
The average salary of all employees=Rs2150
Formula Used:
Allegation rule to find the ratio
Solution:
Allegation rule:
Ratio of number of employees of second to one =  $$(C_1-C_m):(C_m-C_2)$$​​
Where $$C_1$$​ and $$C_2$$ are averages and C_m is the mean of the averages.
Here $$C_1= Rs3950 , C_2= Rs1850$$​ and C_m =Rs2150
(3950-2150):(2150-1850) =1800:300 =6:1
1≡12
6≡6×12
=72
Total number of employees = 72+12= 84