The ratio of the number of blue erasers to red erasers is 9 : 4. After Ian gives away 30 blue erasers and buys another 40 red erasers, there is equal number of blue erasers and red erasers. How many erasers does Ian have now?
| |
Blue |
Red |
| Before |
9 u |
4 u |
| Change |
- 30 |
+ 40 |
| After |
9 u - 30 |
4 u + 40 |
The number of blue erasers and red erasers in the end is the same.
9 u - 30 = 4 u + 40
9 u - 4 u = 40 + 30
5 u = 70
1 u = 70 ÷ 5 = 14
Number of erasers that Ian has now
= 9 u - 30 + 4 u + 40
= 9 u + 4 u - 30 + 40
= 13 u + 10
= 13 x 14 + 10
= 182 + 10
= 192
Answer(s): 192
