The average amount of money collected by a group of pupils at a flag day event was $108. When another 10 pupils turned up to help, the total amount donated increased by $500 and the average amount of money collected became $79. 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 |
108 |
79 |
Total Value |
108 u + 500 |
79 u + 790 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 108
= 108 u
Total amount collected by the pupils in the end
= 79 x (1 u + 10)
= 79 u + 790
108 u + 500 = 79 u + 790
108 u - 79 u = 790 - 500
29 u = 290
1 u = 290 ÷ 29 = 10
Number of pupils in the end
= 1 u + 10
= 10 + 10
= 20
Answer(s): 20