The average amount of money collected by a group of pupils at a flag day event was $118. When another 12 pupils turned up to help, the total amount donated increased by $618 and the average amount of money collected became $80. How many pupils were there in the group in the end?
| |
Number of pupils
at first |
Number of pupils
in the end |
| Number |
1 u |
1 u + 12 |
| Value |
118 |
80 |
| Total Value |
118 u + 618 |
80 u + 960 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 118
= 118 u
Total amount collected by the pupils in the end
= 80 x (1 u + 12)
= 80 u + 960
118 u + 618 = 80 u + 960
118 u - 80 u = 960 - 618
38 u = 342
1 u = 342 ÷ 38 = 9
Number of pupils in the end
= 1 u + 12
= 9 + 12
= 21
Answer(s): 21
