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 $610 and the average amount of money collected became $90. How many pupils were there in the group in the end?
|
Number of pupils at first |
Number of pupils in the end |
Number |
1 u |
1 u + 14 |
Value |
100 |
90 |
Total Value |
100 u + 610 |
90 u + 1260 |
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 + 14)
= 90 u + 1260
100 u + 610 = 90 u + 1260
100 u - 90 u = 1260 - 610
10 u = 650
1 u = 650 ÷ 10 = 65
Number of pupils in the end
= 1 u + 14
= 65 + 14
= 79
Answer(s): 79