Cathy has a bag containing some black and blue erasers. If she removes 5 black erasers, 25% of the erasers in the bag are blue. If she adds another 8 blue erasers, 50% of the erasers in the bag are blue. How many black erasers are in the bag?
| |
Black erasers |
Blue erasers |
| Before |
3 u + 5 |
1 u |
| Change 1 |
- 5 |
|
| After 1 |
3x1 =
3 u |
1x1 =
1 u |
| Change 2 |
|
+ 8 |
| After 2 |
1x3 =
3 u |
1x3 =
3 u |
25% =
25100 =
1450% =
50100 =
12The number of black erasers remains unchanged at the second change when she adds another 8 blue erasers. Make the number of black erasers the same at the second change. LCM of 3 and 1 is 3.
Number of blue erasers added
= 3 u - 1 u
= 2 u
2 u = 8
1 u = 8 ÷ 2 = 4
Number of black erasers at first
= 3 u + 5
= 3 x 4 + 5
= 12 + 5
= 17
Answer(s): 17
