The ratio of the number of blue pens to green pens is 3 : 1. After Pierre gives away 40 blue pens and buys another 90 green pens, there is equal number of blue pens and green pens. How many pens does Pierre have now?
| |
Blue |
Green |
| Before |
3 u |
1 u |
| Change |
- 40 |
+ 90 |
| After |
3 u - 40 |
1 u + 90 |
The number of blue pens and green pens in the end is the same.
3 u - 40 = 1 u + 90
3 u - 1 u = 90 + 40
2 u = 130
1 u = 130 ÷ 2 = 65
Number of pens that Pierre has now
= 3 u - 40 + 1 u + 90
= 3 u + 1 u - 40 + 90
= 4 u + 50
= 4 x 65 + 50
= 260 + 50
= 310
Answer(s): 310
