The average amount of money collected by a group of pupils at a flag day event was $101. When another 15 pupils turned up to help, the total amount donated increased by $802 and the average amount of money collected became $78. 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 |
101 |
78 |
| Total Value |
101 u + 802 |
78 u + 1170 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 101
= 101 u
Total amount collected by the pupils in the end
= 78 x (1 u + 15)
= 78 u + 1170
101 u + 802 = 78 u + 1170
101 u - 78 u = 1170 - 802
23 u = 368
1 u = 368 ÷ 23 = 16
Number of pupils at first
= 1 u
= 16
Answer(s): 16
