Some pupils board a school bus.
At Bus Stop A,
13 of them alight
and 11 pupils board.
At Bus Stop B,
13 of the pupils alight
and 8 board.
If there are 18 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 + 11 |
|
After 1 |
2 u + 11 |
3 p |
Change 2 At Bus Stop B |
|
- 1 p + 8 |
After 2 |
|
18 |
Working backwards.
Number of pupils in the end = 18
3 p - 1 p = 18 - 8
2 p = 10
1 p = 10 ÷ 2 = 5
3 p = 3 x 5
3 p = 15
2 u + 11 = 3 p
2 u + 11 = 15
2 u = 15 - 11
2 u = 4
1 u = 4 ÷ 2 = 2
Total number of pupils at first
= 3 u
= 3 x 2
= 6
Answer(s): 6