The ratio of the number of blue stamps to green stamps is 3 : 1. After Ian gives away 20 blue stamps and buys another 60 green stamps, there is equal number of blue stamps and green stamps. How many stamps does Ian have now?
| |
Blue |
Green |
| Before |
3 u |
1 u |
| Change |
- 20 |
+ 60 |
| After |
3 u - 20 |
1 u + 60 |
The number of blue stamps and green stamps in the end is the same.
3 u - 20 = 1 u + 60
3 u - 1 u = 60 + 20
2 u = 80
1 u = 80 ÷ 2 = 40
Number of stamps that Ian has now
= 3 u - 20 + 1 u + 60
= 3 u + 1 u - 20 + 60
= 4 u + 40
= 4 x 40 + 40
= 160 + 40
= 200
Answer(s): 200
