The ratio of the number of blue pens to green pens is 9 : 2. After Carl gives away 20 blue pens and buys another 50 green pens, there is equal number of blue pens and green pens. How many pens does Carl have now?
| |
Blue |
Green |
| Before |
9 u |
2 u |
| Change |
- 20 |
+ 50 |
| After |
9 u - 20 |
2 u + 50 |
The number of blue pens and green pens in the end is the same.
9 u - 20 = 2 u + 50
9 u - 2 u = 50 + 20
7 u = 70
1 u = 70 ÷ 7 = 10
Number of pens that Carl has now
= 9 u - 20 + 2 u + 50
= 9 u + 2 u - 20 + 50
= 11 u + 30
= 11 x 10 + 30
= 110 + 30
= 140
Answer(s): 140
