The average weight of a certain number of children in a group was 31 kg. If 11 children of average weight 32.5 kg joined the group, then the average weight of all the children would increase by 0.25 kg. The number of children initially in the group was:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 55
Given:
The average weight of a certain number of children in a group was 31 kg.
If 11 children of average weight 32.5 kg joined the group, then the average weight of all the children would increase by 0.25 kg
Formula used:
Average = sum of observations/number of observations ----- (1)
Calculations:
Let the number of children be x.
Sum of the weight of children initially = 31x
Sum of weight of 11 children = 32.5 × 11 = 357.5
According to the question;
⇒ 31x + 357.5 = (x + 11) × (31 + 0.25)
⇒ 31x + 357.5 = 31.25x + 343.75
⇒ 31.25x - 31x = 357.5 - 343.75
⇒ 0.25x = 13.75
⇒ x = 55