Elyse has a bag containing some silver and blue pens. If she removes 5 silver pens, 10% of the pens in the bag are blue. If she adds another 10 blue pens, 40% of the pens in the bag are blue. How many silver pens are in the bag?
| |
Silver pens |
Blue pens |
| Before |
9 u + 5 |
1 u |
| Change 1 |
- 5 |
|
| After 1 |
9x1 =
9 u |
1x1 =
1 u |
| Change 2 |
|
+ 10 |
| After 2 |
3x3 =
9 u |
2x3 =
6 u |
10% =
10100 =
11040% =
40100 =
25The number of silver pens remains unchanged at the second change when she adds another 10 blue pens. Make the number of silver pens the same at the second change. LCM of 9 and 3 is 9.
Number of blue pens added
= 6 u - 1 u
= 5 u
5 u = 10
1 u = 10 ÷ 5 = 2
Number of silver pens at first
= 9 u + 5
= 9 x 2 + 5
= 18 + 5
= 23
Answer(s): 23
