The average amount of money collected by a group of pupils at a flag day event was $100. When another 12 pupils turned up to help, the total amount donated increased by $580 and the average amount of money collected became $90. 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 + 12 |
Value |
100 |
90 |
Total Value |
100 u + 580 |
90 u + 1080 |
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
= 90 x (1 u + 12)
= 90 u + 1080
100 u + 580 = 90 u + 1080
100 u - 90 u = 1080 - 580
10 u = 500
1 u = 500 ÷ 10 = 50
Number of pupils at first
= 1 u
= 50
Answer(s): 50