Bryan and Adam have a total of $81.
Bryan spends
13 of his money and
Adam spends
18 of his money.
They spend $12 altogether.
- How much does Bryan have at first?
- How much does Adam have in the end?
|
Bryan |
Adam |
Before |
3 u |
8 p |
Change |
- 1 u |
- 1 p |
After |
2 u |
7 p |
(a)
Amount that Bryan has at first = 3 u
Amount that Adam has at first = 8 p
Total amount that they have = 3 u + 8 p = 81 --- (1)
Total amount that they spend = 1 u + 1 p = 12 --- (2)
(2)
x 8 8 u + 8 p = 96 --- (3)
(3) - (1)
(8 u + 8 p) - (3 u + 8 p) = 96 - 81
8 u + 8 p - 3 u - 8 p = 96 - 81
8 u - 3 u + 8 p - 8 p = 15
8 u - 3 u = 15
5 u = 15
1 u = 15 ÷ 5 = 3
Substitute 1 u = 3 into (1).
3 u + 8 p = 81
3 x 3 + 8 p = 81
9 + 8 p = 81
8 p = 81 - 9 = 72
1 p = 72 ÷ 8 = 9
Amount that Bryan has at first
= 3 u
= 3 x 3
= $9
(b)
Amount that Adam has in the end
= 8 p - 1 p
= 7 p
= 7 x 9
= $63
Answer(s): (a) $9; (b) $63