David had $150 less than Vincent. If Vincent spends $70 and David's mother gave David $120, Vincent will have
13 as much money as David. How much money did David and Vincent have?
| |
Make p the same
(1)x3 = (3) |
David
(1) |
Vincent
(2) |
| Before |
3 u |
1 u |
1 u + 150 |
| Change |
- 210 |
- 70 |
+ 120 |
| After |
3 p |
1 p |
3 p |
Since David had $150 less than Vincent, this means Vincent had $150 more than David.
1 u - 70 = 1 p --- (1)
1 u + 150 + 120 = 3 p
1 u + 270 =
3 p --- (2)
Make p the same.
(1)
x3
3 u - 210 =
3 p --- (3)
(3) = (2)
3 u - 210 = 1 u + 270
3 u - 1 u = 270 + 210
2 u = 480
1 u = 480 ÷ 2 = 240
Total amount that David and Vincent had
= 1 u + 1 u + 150
= 2 u + 150
= 2 x 240 + 150
= 480 + 150
= $630
Answer(s): $630
