The ratio of the number of red stamps to blue stamps is 9 : 7. After Ethan gives away 50 red stamps and buys another 70 blue stamps, there is equal number of red stamps and blue stamps. How many stamps does Ethan have now?
| |
Red |
Blue |
| Before |
9 u |
7 u |
| Change |
- 50 |
+ 70 |
| After |
9 u - 50 |
7 u + 70 |
The number of red stamps and blue stamps in the end is the same.
9 u - 50 = 7 u + 70
9 u - 7 u = 70 + 50
2 u = 120
1 u = 120 ÷ 2 = 60
Number of stamps that Ethan has now
= 9 u - 50 + 7 u + 70
= 9 u + 7 u - 50 + 70
= 16 u + 20
= 16 x 60 + 20
= 960 + 20
= 980
Answer(s): 980
