The ratio of the number of red stamps to green stamps is 7 : 5. After Owen gives away 40 red stamps and buys another 80 green stamps, there is equal number of red stamps and green stamps. How many stamps does Owen have now?
|
Red |
Green |
Before |
7 u |
5 u |
Change |
- 40 |
+ 80 |
After |
7 u - 40 |
5 u + 80 |
The number of red stamps and green stamps in the end is the same.
7 u - 40 = 5 u + 80
7 u - 5 u = 80 + 40
2 u = 120
1 u = 120 ÷ 2 = 60
Number of stamps that Owen has now
= 7 u - 40 + 5 u + 80
= 7 u + 5 u - 40 + 80
= 12 u + 40
= 12 x 60 + 40
= 720 + 40
= 760
Answer(s): 760