Eva has a bag containing some gold and green pens. If she adds in 17 gold pens, 10% of the pens in the bag are green. If she adds in another 40 green pens, 40% of the pens in the bag are green. How many gold pens are in the bag?
| |
Gold pens |
Green pens |
| Before |
9 u - 17 |
1 u |
| Change 1 |
+ 17 |
|
| After 1 |
9x1 =
9 u |
1x1 =
1 u |
| Change 2 |
|
+ 40 |
| After 2 |
3x3 =
9 u |
2x3 =
6 u |
10% =
10100 =
11040% =
40100 =
25The number of gold pens remains unchanged at the second change when she adds in another 40 green pens. Make the number of gold pens the same at the second change. LCM of 9 and 3 is 9.
Number of green pens added
= 6 u - 1 u
= 5 u
5 u = 40
1 u = 40 ÷ 5 = 8
Number of gold pens at first
= 9 u - 17
= 9 x 8 - 17
= 72 - 17
= 55
Answer(s): 55
