The average amount of money collected by a group of pupils at a flag day event was $108. When another 13 pupils turned up to help, the total amount donated increased by $567 and the average amount of money collected became $81. 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 + 13 |
Value |
108 |
81 |
Total Value |
108 u + 567 |
81 u + 1053 |
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
= 81 x (1 u + 13)
= 81 u + 1053
108 u + 567 = 81 u + 1053
108 u - 81 u = 1053 - 567
27 u = 486
1 u = 486 ÷ 27 = 18
Number of pupils at first
= 1 u
= 18
Answer(s): 18