The average amount of money collected by a group of pupils at a flag day event was $100. When another 15 pupils turned up to help, the total amount donated increased by $630 and the average amount of money collected became $70. 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 + 15 |
Value |
100 |
70 |
Total Value |
100 u + 630 |
70 u + 1050 |
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
= 70 x (1 u + 15)
= 70 u + 1050
100 u + 630 = 70 u + 1050
100 u - 70 u = 1050 - 630
30 u = 420
1 u = 420 ÷ 30 = 14
Number of pupils in the end
= 1 u + 15
= 14 + 15
= 29
Answer(s): 29