In a school 3 classes took the same exam. Class A had 30 students and average mark for the class was 66.?

Question

Class B 22 students average mark was 54. Class C had 20 students. The average obtained by all the pupils together was 61.5 . Calculate the average mark of Class C.

Answer 1

ANSWER-63

PROCEDURE-

TOTAL MARKS OF CLASS-A=AVG. MARKS*NO. OF STUDENTS

                                           =66*30=1980

TOTAL MARKS OF CLASS-B=54*22=1188

TOTAL MARKS OF CLASS-A,B,C=61.5*(30+22+20)=61.5*72=4428

TOTAL MARKS OF CLASS-C=TOTAL MARKS OF CLASS-A,B,C-TOTAL MARKS OF CLASS-A-TOTAL MARKS OF CLASS-B

TOTAL MARKS OF CLASS-C=4428-1980-1188=1260

TOTAL MARKS OF CLASS-C=AVG. MARKS*NO. OF STUDENTS

1260=X*20

X=1260/20

X=63

IE-AVG. MARKS OF CLASS-C=63