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1. Three maths classes: X, Y, and Z take an algebra test. The average score of class X is 83. The average score of class Y is 76. The average score of class Z is 85. The average score of class X and Y is 79 and the average score of class Y and Z is 81. What is the average score of the combined classes X, Y, and Z?
- A. 81
- B. 81
- C. 81
- D. 81
Answer: Option B
Explanation:
According to question,
(i) (83x + 76y)/( x + y )=79
⇒ x = 43y
(ii) (76y + 85z)/(y + z) = 81
z = 45y
Average of all 3 = (83x + 76y + 85z)/(x + y + z)
=81.5
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