The ratio of the number of blue pens to green pens is 8 : 3. After Ben gives away 20 blue pens and buys another 30 green pens, there is equal number of blue pens and green pens. How many pens does Ben have now?
| |
Blue |
Green |
| Before |
8 u |
3 u |
| Change |
- 20 |
+ 30 |
| After |
8 u - 20 |
3 u + 30 |
The number of blue pens and green pens in the end is the same.
8 u - 20 = 3 u + 30
8 u - 3 u = 30 + 20
5 u = 50
1 u = 50 ÷ 5 = 10
Number of pens that Ben has now
= 8 u - 20 + 3 u + 30
= 8 u + 3 u - 20 + 30
= 11 u + 10
= 11 x 10 + 10
= 110 + 10
= 120
Answer(s): 120
