The average amount of money collected by a group of pupils at a flag day event was $109. When another 13 pupils turned up to help, the total amount donated increased by $581 and the average amount of money collected became $71. 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 + 13 |
| Value |
109 |
71 |
| Total Value |
109 u + 581 |
71 u + 923 |
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
= 71 x (1 u + 13)
= 71 u + 923
109 u + 581 = 71 u + 923
109 u - 71 u = 923 - 581
38 u = 342
1 u = 342 ÷ 38 = 9
Number of pupils in the end
= 1 u + 13
= 9 + 13
= 22
Answer(s): 22
