Some pupils board a school bus.
At Bus Stop A,
13 of them alight
and 4 pupils board.
At Bus Stop B,
25 of the pupils alight
and 9 board.
If there are 15 pupils on the bus now,
how many pupils are on the bus at first?
|
Number of pupils |
Before |
3 u |
|
Change 1 At Bus Stop A |
- 1 u + 4 |
|
After 1 |
2 u + 4 |
5 p |
Change 2 At Bus Stop B |
|
- 2 p + 9 |
After 2 |
|
15 |
Working backwards.
Number of pupils in the end = 15
5 p - 2 p = 15 - 9
3 p = 6
1 p = 6 ÷ 3 = 2
5 p = 5 x 2
5 p = 10
2 u + 4 = 5 p
2 u + 4 = 10
2 u = 10 - 4
2 u = 6
1 u = 6 ÷ 2 = 3
Total number of pupils at first
= 3 u
= 3 x 3
= 9
Answer(s): 9