Multiple choice

The average weight of P and Q is 30 kg. and that of Q and R is 26kg. The difference of the weights of P and R is

  1. 2 kg.

  2. 4 kg.

  3. 6 kg.

  4. 8 kg.

  5. 10 kg.
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D Correct answer
Explanation

Let P, Q, R be the weights. (P + Q)/2 = 30, so P + Q = 60. (Q + R)/2 = 26, so Q + R = 52. Subtracting: (P + Q) - (Q + R) = P - R = 60 - 52 = 8. The difference |P - R| = 8 kg. This uses the concept that average × number of items = sum.

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