The average amount of money collected by a group of students at a flag day event was $114. When another 15 students turned up to help, the total amount donated increased by $522 and the average amount of money collected became $78. How many students were there in the group at first?
| |
Number of students
at first |
Number of students
in the end |
| Number |
1 u |
1 u + 15 |
| Value |
114 |
78 |
| Total Value |
114 u + 522 |
78 u + 1170 |
Number of students at first = 1 u
Total amount collected by the students at first
= 1 u x 114
= 114 u
Total amount collected by the students in the end
= 78 x (1 u + 15)
= 78 u + 1170
114 u + 522 = 78 u + 1170
114 u - 78 u = 1170 - 522
36 u = 648
1 u = 648 ÷ 36 = 18
Number of students at first
= 1 u
= 18
Answer(s): 18
