The average amount of money collected by a group of pupils at a flag day event was $109. When another 15 pupils turned up to help, the total amount donated increased by $942 and the average amount of money collected became $88. 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 + 15 |
| Value |
109 |
88 |
| Total Value |
109 u + 942 |
88 u + 1320 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 109
= 109 u
Total amount collected by the pupils in the end
= 88 x (1 u + 15)
= 88 u + 1320
109 u + 942 = 88 u + 1320
109 u - 88 u = 1320 - 942
21 u = 378
1 u = 378 ÷ 21 = 18
Number of pupils in the end
= 1 u + 15
= 18 + 15
= 33
Answer(s): 33
