The average amount of money collected by a group of pupils at a flag day event was $111. When another 10 pupils turned up to help, the total amount donated increased by $610 and the average amount of money collected became $86. 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 + 10 |
Value |
111 |
86 |
Total Value |
111 u + 610 |
86 u + 860 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 111
= 111 u
Total amount collected by the pupils in the end
= 86 x (1 u + 10)
= 86 u + 860
111 u + 610 = 86 u + 860
111 u - 86 u = 860 - 610
25 u = 250
1 u = 250 ÷ 25 = 10
Number of pupils in the end
= 1 u + 10
= 10 + 10
= 20
Answer(s): 20