The average amount of money collected by a group of pupils at a flag day event was $107. When another 11 pupils turned up to help, the total amount donated increased by $568 and the average amount of money collected became $78. 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 + 11 |
Value |
107 |
78 |
Total Value |
107 u + 568 |
78 u + 858 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 107
= 107 u
Total amount collected by the pupils in the end
= 78 x (1 u + 11)
= 78 u + 858
107 u + 568 = 78 u + 858
107 u - 78 u = 858 - 568
29 u = 290
1 u = 290 ÷ 29 = 10
Number of pupils in the end
= 1 u + 11
= 10 + 11
= 21
Answer(s): 21