Multiple choice

The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man E, whose weight is 3 kg more than that of D, replaces A, then the average weight of B, C, D and E becomes 79 kg. What is the weight of A?

  1. 70 kg

  2. 72 kg

  3. 75 kg

  4. 80 kg
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A+B+C = 84*3 = 252. A+B+C+D = 80*4 = 320. D = 320 - 252 = 68. E = D + 3 = 71. B+C+D+E = 79*4 = 316. B+C = 316 - 68 - 71 = 177. A = 252 - (B+C) = 252 - 177 = 75.

AI explanation

The total weight of A, B and C is 3 multiplied by 84, which is 252 kg. When D joins, the total weight of the four men becomes 4 multiplied by 80, or 320 kg, making D's weight 68 kg. Since E weighs 3 kg more than D, E weighs 71 kg, and the total weight of B, C, D and E is 4 multiplied by 79, or 316 kg. Comparing the group B, C, D to the group B, C, D, E shows E adds 71 kg, meaning B, C and D weigh 245 kg, which is 5 kg less than the original 252 kg for A, B and C, so A weighs 75 kg.

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