Fiona has a bag containing some purple and yellow pens. If she removes 8 purple pens, 30% of the pens in the bag are yellow. If she adds another 50 yellow pens, 40% of the pens in the bag are yellow. How many purple pens are in the bag?
| |
Purple pens |
Yellow pens |
| Before |
21 u + 8 |
9 u |
| Change 1 |
- 8 |
|
| After 1 |
7x3 =
21 u |
3x3 =
9 u |
| Change 2 |
|
+ 50 |
| After 2 |
3x7 =
21 u |
2x7 =
14 u |
30% =
30100 =
31040% =
40100 =
25The number of purple pens remains unchanged at the second change when she adds another 50 yellow pens. Make the number of purple pens the same at the second change. LCM of 7 and 3 is 21.
Number of yellow pens added
= 14 u - 9 u
= 5 u
5 u = 50
1 u = 50 ÷ 5 = 10
Number of purple pens at first
= 21 u + 8
= 21 x 10 + 8
= 210 + 8
= 218
Answer(s): 218
