Marion has a bag containing some purple and gold pens. If she adds in 20 purple pens, 10% of the pens in the bag are gold. If she adds in another 40 gold pens, 50% of the pens in the bag are gold. How many purple pens are in the bag?
| |
Purple pens |
Gold pens |
| Before |
9 u - 20 |
1 u |
| Change 1 |
+ 20 |
|
| After 1 |
9x1 =
9 u |
1x1 =
1 u |
| Change 2 |
|
+ 40 |
| After 2 |
1x9 =
9 u |
1x9 =
9 u |
10% =
10100 =
11050% =
50100 =
12The number of purple pens remains unchanged at the second change when she adds in another 40 gold pens. Make the number of purple pens the same at the second change. LCM of 9 and 1 is 9.
Number of gold pens added
= 9 u - 1 u
= 8 u
8 u = 40
1 u = 40 ÷ 8 = 5
Number of purple pens at first
= 9 u - 20
= 9 x 5 - 20
= 45 - 20
= 25
Answer(s): 25
