The ratio of the number of blue stamps to green stamps is 7 : 4. After Tommy gives away 50 blue stamps and buys another 70 green stamps, there is equal number of blue stamps and green stamps. How many stamps does Tommy have now?
|
Blue |
Green |
Before |
7 u |
4 u |
Change |
- 50 |
+ 70 |
After |
7 u - 50 |
4 u + 70 |
The number of blue stamps and green stamps in the end is the same.
7 u - 50 = 4 u + 70
7 u - 4 u = 70 + 50
3 u = 120
1 u = 120 ÷ 3 = 40
Number of stamps that Tommy has now
= 7 u - 50 + 4 u + 70
= 7 u + 4 u - 50 + 70
= 11 u + 20
= 11 x 40 + 20
= 440 + 20
= 460
Answer(s): 460