Some pupils board a school bus.
At Bus Stop A,
13 of them alight
and 12 pupils board.
At Bus Stop B,
59 of the pupils alight
and 12 board.
If there are 20 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 + 12 |
|
After 1 |
2 u + 12 |
9 p |
Change 2 At Bus Stop B |
|
- 5 p + 12 |
After 2 |
|
20 |
Working backwards.
Number of pupils in the end = 20
9 p - 5 p = 20 - 12
4 p = 8
1 p = 8 ÷ 4 = 2
9 p = 9 x 2
9 p = 18
2 u + 12 = 9 p
2 u + 12 = 18
2 u = 18 - 12
2 u = 6
1 u = 6 ÷ 2 = 3
Total number of pupils at first
= 3 u
= 3 x 3
= 9
Answer(s): 9