The average amount of money collected by a group of pupils at a flag day event was $110. When another 15 pupils turned up to help, the total amount donated increased by $710 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 + 15 |
Value |
110 |
90 |
Total Value |
110 u + 710 |
90 u + 1350 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 110
= 110 u
Total amount collected by the pupils in the end
= 90 x (1 u + 15)
= 90 u + 1350
110 u + 710 = 90 u + 1350
110 u - 90 u = 1350 - 710
20 u = 640
1 u = 640 ÷ 20 = 32
Number of pupils in the end
= 1 u + 15
= 32 + 15
= 47
Answer(s): 47