The average of two numbers A and B is 20, B and C is 19 and C and A is 21. Then the value of A is :दो संख्याओं A व B का औसत 20, B तथा C संख्याओं का औसत 19 तथा C व A का औसत 21 हो, तो A का मान है :

1. A24
2. B22
3. C20
4. D18

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Correct answer: B. 22

Explanation

A + B = 40, B + C = 38, C + A = 42. Adding, 2(A + B + C) = 120, so A + B + C = 60. Then A = 60 − (B + C) = 60 − 38 = 22.A + B = 40, B + C = 38, C + A = 42। जोड़ने पर 2(A + B + C) = 120, अतः A + B + C = 60। तब A = 60 − (B + C) = 60 − 38 = 22।