The average weight of some persons in a group is 72 kg. When 5 persons with average weight 66.6 kg join and 12 persons with average weight 75 kg leave the group, the average weight of the persons in the group decreases by 1.65 kg. How many persons were there in the group initially?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 48
Let the initial number of persons be = x
New total weight;
x × 72 + 5 × 66.6 - 13 × 75 = (x + 5 - 13) × (72 - 1.65)
⇒ 72x + 333 - 975 = (x - 8) × 70.35
⇒ 72x - 642 = 70.35x - 562.8
⇒ 72x - 70.35x = 642 - 562.8
⇒ 1.65x = 79.2
⇒ x = 79.2/1.65
Inital number of persons were 48