The ratio of the number of green erasers to red erasers is 5 : 3. After Andy gives away 50 green erasers and buys another 80 red erasers, there is equal number of green erasers and red erasers. How many erasers does Andy have now?
| |
Green |
Red |
| Before |
5 u |
3 u |
| Change |
- 50 |
+ 80 |
| After |
5 u - 50 |
3 u + 80 |
The number of green erasers and red erasers in the end is the same.
5 u - 50 = 3 u + 80
5 u - 3 u = 80 + 50
2 u = 130
1 u = 130 ÷ 2 = 65
Number of erasers that Andy has now
= 5 u - 50 + 3 u + 80
= 5 u + 3 u - 50 + 80
= 8 u + 30
= 8 x 65 + 30
= 520 + 30
= 550
Answer(s): 550
