The ratio of the number of red erasers to blue erasers is 9 : 7. After Dylan gives away 10 red erasers and buys another 60 blue erasers, there is equal number of red erasers and blue erasers. How many erasers does Dylan have now?
| |
Red |
Blue |
| Before |
9 u |
7 u |
| Change |
- 10 |
+ 60 |
| After |
9 u - 10 |
7 u + 60 |
The number of red erasers and blue erasers in the end is the same.
9 u - 10 = 7 u + 60
9 u - 7 u = 60 + 10
2 u = 70
1 u = 70 ÷ 2 = 35
Number of erasers that Dylan has now
= 9 u - 10 + 7 u + 60
= 9 u + 7 u - 10 + 60
= 16 u + 50
= 16 x 35 + 50
= 560 + 50
= 610
Answer(s): 610
