The average weight of two persons A and B is 70 kg. Another person C joins A and B and the average weight now becomes 72 kg. If another person D, whose weight is 2 kg less than that of C, replaces A, then the average weight of B, C and D becomes 70 kg. Find the weight of A (in kg).
Show answer & explanation
Correct answer: C
Explanation
The corrct answe is option 3 i.e 80kg.
Average weight of A and B = 70 kg ⇒ A + B = 2 × 70 = 140 kg
When C joins A and B, average = 72 kg ⇒ (A + B + C) = 3 × 72 = 216 kg
From earlier, A + B = 140 So, C = 216 - 140 = 76 kg
Person D replaces A and D’s weight = C - 2 = 76 - 2 = 74 kg
New group: B, C, and D
Total weight = 3 × 70 = 210 kg
⇒ B + C + D = 210
⇒ B = 210 - 76 - 74 = 60 kg
Now from earlier A + B = 140
A = 140 - 60 = 80 kg