Ben and Billy went shopping with a total amount of $468. They had $390 left after shopping. Ben's remaining money was 4 times the amount he paid for. Billy's remaining money was 6 times the amount he had spent.
- How much did Billy spend?
- How much did Billy bring along for shopping?
| |
Ben |
Billy |
Total |
| Before |
5 u |
7 p |
468 |
| Change |
- 1 u |
- 1 p |
- 78 |
| After |
4 u |
6 p |
390 |
(a)
Amount that Ben and Billy spent
= 468 - 390
= $78
Amount that Ben and Billy spent
= 1 u + 1 p
1 u + 1 p = 78
1 u = 78 - 1 p --- (1)
Amount that Ben and Billy had left
= 4 u + 6 p
4 u + 6 p = 390
4 u = 390 - 6 p --- (2)
Make u the same.
(1)
x 4 4 u = 312 - 4 p --- (3)
(3) = (2)
312 - 4 p = 390 - 6 p
6 p - 4 p = 390 - 312
2 p = 78
1 p = 78 ÷ 2 = 39
Amount that Billy spent = $39
(b)
Amount that Billy brought along
= 7 p
= 7 x 39
= $273
Answer(s): (a) $39; (b) $273
