The average amount of money collected by a group of pupils at a flag day event was $100. When another 14 pupils turned up to help, the total amount donated increased by $618 and the average amount of money collected became $77. 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 + 14 |
Value |
100 |
77 |
Total Value |
100 u + 618 |
77 u + 1078 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 100
= 100 u
Total amount collected by the pupils in the end
= 77 x (1 u + 14)
= 77 u + 1078
100 u + 618 = 77 u + 1078
100 u - 77 u = 1078 - 618
23 u = 460
1 u = 460 ÷ 23 = 20
Number of pupils at first
= 1 u
= 20
Answer(s): 20