The ratio of the number of blue pens to green pens is 9 : 7. After Pierre gives away 10 blue pens and buys another 60 green pens, there is equal number of blue pens and green pens. How many pens does Pierre have now?
| |
Blue |
Green |
| Before |
9 u |
7 u |
| Change |
- 10 |
+ 60 |
| After |
9 u - 10 |
7 u + 60 |
The number of blue pens and green pens in the end is the same.
9 u - 10 = 7 u + 60
9 u - 7 u = 60 + 10
2 u = 70
1 u = 70 ÷ 2 = 35
Number of pens that Pierre has now
= 9 u - 10 + 7 u + 60
= 9 u + 7 u - 10 + 60
= 16 u + 50
= 16 x 35 + 50
= 560 + 50
= 610
Answer(s): 610
