CAT Exam

Three classes A,B & C take the test.The average score of class A,B & C is 83, 76 & 85 respectively. The average score of all students of class A & B together is 79 and the average score of all students of class B & C together is 81. What is the average of all the three classes?

Read Solution (Total 1)

Let no of people in X,Y,Z be x,y,z
total x = 83x
total y = 76y
total z = 85z

total(x+y) = 79(x+y)
total(y+z) = 81(y+z)

implies
83x + 76y = 79(x+y) --------1
76y + 85z = 81(y+z) --------2

1 is 3y=4x
2 is 5y=4z

average of 3 classes = total( x + y + z )/( x + y + z)

= (83x+76y+85z)/( x + y + z)

= 978/12

= 81.5
12 years agoHelpfull: Yes(4) No(2)

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