Multiple choice

The average weight of three men $'X', 'Y'$ and $'Z'$ is $75$ kgs. Another mand $'A'$ joins the group and the average weight now becomes $80\ kgs$. If another person $'B'$ whose weight is $5\ kgs$ more than $'A$ replaces $'X'$, then the average weight of $'Y', 'Z', 'A'$ and $'B'$ will be $85\ kgs$. What is the weight of $'X'$?

  1. $84\ kgs$
  2. $82\ kgs$
  3. $78\ kgs$
  4. $80\ kgs$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The total weight of X, Y, and Z is 3 x 75 = 225 kg. After A joins, the total is 4 x 80 = 320 kg, so A weighs 95 kg and B weighs 100 kg. The final total is 4 x 85 = 340 kg, giving X = 225 - (340 - 95 - 100) = 80 kg.

AI explanation

The total weight of X, Y, and Z is 3 times 75, which is 225 kg. When A joins, the total weight becomes 4 times 80, which is 320 kg, making A's weight 95 kg. Since B's weight is 5 kg more than A, B weighs 100 kg. The new average of Y, Z, A, and B is 85 kg, so their total weight is 4 times 85, which is 340 kg; equating this to (Y + Z) + 95 + 100 gives Y + Z = 145 kg. Subtracting this from the initial total, X equals 225 minus 145, which is 80 kgs.

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