The ratio of the number of green erasers to blue erasers is 3 : 1. After Eric gives away 20 green erasers and buys another 90 blue erasers, there is equal number of green erasers and blue erasers. How many erasers does Eric have now?
|
Green |
Blue |
Before |
3 u |
1 u |
Change |
- 20 |
+ 90 |
After |
3 u - 20 |
1 u + 90 |
The number of green erasers and blue erasers in the end is the same.
3 u - 20 = 1 u + 90
3 u - 1 u = 90 + 20
2 u = 110
1 u = 110 ÷ 2 = 55
Number of erasers that Eric has now
= 3 u - 20 + 1 u + 90
= 3 u + 1 u - 20 + 90
= 4 u + 70
= 4 x 55 + 70
= 220 + 70
= 290
Answer(s): 290