Some pupils board a school bus.
At Bus Stop A,
15 of them alight
and 2 pupils board.
At Bus Stop B,
13 of the pupils alight
and 3 board.
If there are 15 pupils on the bus now,
how many pupils are on the bus at first?
|
Number of pupils |
Before |
5 u |
|
Change 1 At Bus Stop A |
- 1 u + 2 |
|
After 1 |
4 u + 2 |
3 p |
Change 2 At Bus Stop B |
|
- 1 p + 3 |
After 2 |
|
15 |
Working backwards.
Number of pupils in the end = 15
3 p - 1 p = 15 - 3
2 p = 12
1 p = 12 ÷ 2 = 6
3 p = 3 x 6
3 p = 18
4 u + 2 = 3 p
4 u + 2 = 18
4 u = 18 - 2
4 u = 16
1 u = 16 ÷ 4 = 4
Total number of pupils at first
= 5 u
= 5 x 4
= 20
Answer(s): 20