The ratio of the number of red stamps to blue stamps is 7 : 5. After Zeph gives away 10 red stamps and buys another 60 blue stamps, there is equal number of red stamps and blue stamps. How many stamps does Zeph have now?
| |
Red |
Blue |
| Before |
7 u |
5 u |
| Change |
- 10 |
+ 60 |
| After |
7 u - 10 |
5 u + 60 |
The number of red stamps and blue stamps in the end is the same.
7 u - 10 = 5 u + 60
7 u - 5 u = 60 + 10
2 u = 70
1 u = 70 ÷ 2 = 35
Number of stamps that Zeph has now
= 7 u - 10 + 5 u + 60
= 7 u + 5 u - 10 + 60
= 12 u + 50
= 12 x 35 + 50
= 420 + 50
= 470
Answer(s): 470
