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 $785 and the average amount of money collected became $89. 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 |
89 |
Total Value |
100 u + 785 |
89 u + 1335 |
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
= 89 x (1 u + 15)
= 89 u + 1335
100 u + 785 = 89 u + 1335
100 u - 89 u = 1335 - 785
11 u = 550
1 u = 550 ÷ 11 = 50
Number of pupils in the end
= 1 u + 15
= 50 + 15
= 65
Answer(s): 65