Multiple choice

The average weight of X, Y and Z is 74 kg. If the average weight of X and Y be 68 kg and that of Y and Z be 78 kg, then the weight (in kg) of Y is

  1. 72

  2. 70

  3. 68

  4. 66
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The sum of the weights of X, Y, and Z is 74 * 3 = 222 kg. The sum of the weights of X and Y is 136 kg, and the sum of the weights of Y and Z is 156 kg. Adding these two equations gives X + 2Y + Z = 292 kg, and subtracting the total sum of 222 kg leaves the weight of Y as 70 kg.

AI explanation

The total weight of X, Y and Z is 74 multiplied by 3, which is 222 kg. The combined weight of X and Y is 68 multiplied by 2, or 136 kg, and the combined weight of Y and Z is 78 multiplied by 2, or 156 kg. Adding the weights of (X + Y) and (Y + Z) gives 292 kg, and subtracting the total weight of all three gives the weight of Y alone: 292 minus 222 equals 70 kg.

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