The average amount of money collected by a group of pupils at a flag day event was $112. When another 13 pupils turned up to help, the total amount donated increased by $840 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 + 13 |
Value |
112 |
90 |
Total Value |
112 u + 840 |
90 u + 1170 |
Number of pupils at first = 1 u
Total amount collected by the pupils at first
= 1 u x 112
= 112 u
Total amount collected by the pupils in the end
= 90 x (1 u + 13)
= 90 u + 1170
112 u + 840 = 90 u + 1170
112 u - 90 u = 1170 - 840
22 u = 330
1 u = 330 ÷ 22 = 15
Number of pupils in the end
= 1 u + 13
= 15 + 13
= 28
Answer(s): 28