The average amount of money collected by a group of pupils at a flag day event was $108. When another 8 pupils turned up to help, the total amount donated increased by $558 and the average amount of money collected became $90. How many pupils were there in the group at first?
|
Number of pupils at first |
Number of pupils in the end |
Number |
1 u |
1 u + 8 |
Value |
108 |
90 |
Total Value |
108 u + 558 |
90 u + 720 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 108
= 108 u
Total amount collected by the pupils in the end
= 90 x (1 u + 8)
= 90 u + 720
108 u + 558 = 90 u + 720
108 u - 90 u = 720 - 558
18 u = 162
1 u = 162 ÷ 18 = 9
Number of pupils at first
= 1 u
= 9
Answer(s): 9