The average amount of money collected by a group of pupils at a flag day event was $105. When another 9 pupils turned up to help, the total amount donated increased by $561 and the average amount of money collected became $89. 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 + 9 |
| Value |
105 |
89 |
| Total Value |
105 u + 561 |
89 u + 801 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 105
= 105 u
Total amount collected by the pupils in the end
= 89 x (1 u + 9)
= 89 u + 801
105 u + 561 = 89 u + 801
105 u - 89 u = 801 - 561
16 u = 240
1 u = 240 ÷ 16 = 15
Number of pupils in the end
= 1 u + 9
= 15 + 9
= 24
Answer(s): 24
