The average amount of money collected by a group of pupils at a flag day event was $107. When another 15 pupils turned up to help, the total amount donated increased by $615 and the average amount of money collected became $74. 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 + 15 |
Value |
107 |
74 |
Total Value |
107 u + 615 |
74 u + 1110 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 107
= 107 u
Total amount collected by the pupils in the end
= 74 x (1 u + 15)
= 74 u + 1110
107 u + 615 = 74 u + 1110
107 u - 74 u = 1110 - 615
33 u = 495
1 u = 495 ÷ 33 = 15
Number of pupils at first
= 1 u
= 15
Answer(s): 15