# There are three sections A, B and C of class 12 th. If number of stude

^{th}. If number of students in section A, B and C are 95, 209 and 171 respectively and average marks of section A, B and C in an exam are 83, 78 and 85 respectively. What is the average marks of Class 12

^{th}?

A. 80.66

B. 81.52

C. 83.78

D. 80.34

### Right Answer is: B

#### SOLUTION

Given, number of students in section A, B and C are 95, 209 and 171 respectively and average marks of section A, B and C in an exam are 83, 78 and 85 respectively

Average =

⇒ Sum of observations = Average × T

Sum of marks of all students of section A of class 12^{th} =95 × 83 = 7885

Sum of marks of all students of section B of class 12^{th} = 209 × 78 = 16302

Sum of marks of all students of section C of class 12^{th} = 171 × 85 = 14535

Total marks scored by class 12^{th} = 7885 + 16302 + 14535 = 38722

Total number of students = 95 + 209 + 171=475

Average =

So, Required average =

There are three sections A, B and C of class 12 th. If number of stude