The ratio of the number of blue pens to red pens is 7 : 5. After Ahmad gives away 40 blue pens and buys another 90 red pens, there is equal number of blue pens and red pens. How many pens does Ahmad have now?
| |
Blue |
Red |
| Before |
7 u |
5 u |
| Change |
- 40 |
+ 90 |
| After |
7 u - 40 |
5 u + 90 |
The number of blue pens and red pens in the end is the same.
7 u - 40 = 5 u + 90
7 u - 5 u = 90 + 40
2 u = 130
1 u = 130 ÷ 2 = 65
Number of pens that Ahmad has now
= 7 u - 40 + 5 u + 90
= 7 u + 5 u - 40 + 90
= 12 u + 50
= 12 x 65 + 50
= 780 + 50
= 830
Answer(s): 830
