Question

Three maths classes: A, B and C take an algebra test. The 2 score of class A is 83. The 2 score of class B is 76. The 2 score of class C is 85. The 2 score of class A and B is 79 and 2 score of class B and C is 81. What is the 2 score of classes A, B, C ?
A) 81
B) 78
C) 80.5
D) 81.5

Answer 1

According to the given condition
(83x+76y)/(x+y) = 79
on solving x = 3y/4
similarly (76y+85z)/(y+z) = 81
on solving z = 5y/4
average score for all the three classes taken together = 83x+76y+85z/x+y+z

on solving you will get 978y/12y=81.5

Answer 2

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Three maths classes: A, B and C take an algebra test. The 2 score of class A is 83. The 2 score of class B is 76. The 2 score of class C is 85. The 2 score of class A and B is 79 and 2 score of class B and C is 81. What is the 2 score of classes A, B, C ?
A) 81
B) 78
C) 80.5
D) 81.5


$\huge\underline{\green {\textbf{D) 81.5}}}$

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