The ratio of the number of red pens to green pens is 8 : 5. After Jack gives away 40 red pens and buys another 80 green pens, there is equal number of red pens and green pens. How many pens does Jack have now?
| |
Red |
Green |
| Before |
8 u |
5 u |
| Change |
- 40 |
+ 80 |
| After |
8 u - 40 |
5 u + 80 |
The number of red pens and green pens in the end is the same.
8 u - 40 = 5 u + 80
8 u - 5 u = 80 + 40
3 u = 120
1 u = 120 ÷ 3 = 40
Number of pens that Jack has now
= 8 u - 40 + 5 u + 80
= 8 u + 5 u - 40 + 80
= 13 u + 40
= 13 x 40 + 40
= 520 + 40
= 560
Answer(s): 560
