The ratio of the number of green pens to red pens is 8 : 3. After John gives away 60 green pens and buys another 80 red pens, there is equal number of green pens and red pens. How many pens does John have now?
| |
Green |
Red |
| Before |
8 u |
3 u |
| Change |
- 60 |
+ 80 |
| After |
8 u - 60 |
3 u + 80 |
The number of green pens and red pens in the end is the same.
8 u - 60 = 3 u + 80
8 u - 3 u = 80 + 60
5 u = 140
1 u = 140 ÷ 5 = 28
Number of pens that John has now
= 8 u - 60 + 3 u + 80
= 8 u + 3 u - 60 + 80
= 11 u + 20
= 11 x 28 + 20
= 308 + 20
= 328
Answer(s): 328
