Linda has a bag containing some green and black erasers. If she adds in 9 green erasers, 30% of the erasers in the bag are black. If she adds in another 16 black erasers, 50% of the erasers in the bag are black. How many green erasers are in the bag?
| |
Green erasers |
Black erasers |
| Before |
7 u - 9 |
3 u |
| Change 1 |
+ 9 |
|
| After 1 |
7x1 =
7 u |
3x1 =
3 u |
| Change 2 |
|
+ 16 |
| After 2 |
1x7 =
7 u |
1x7 =
7 u |
30% =
30100 =
31050% =
50100 =
12The number of green erasers remains unchanged at the second change when she adds in another 16 black erasers. Make the number of green erasers the same at the second change. LCM of 7 and 1 is 7.
Number of black erasers added
= 7 u - 3 u
= 4 u
4 u = 16
1 u = 16 ÷ 4 = 4
Number of green erasers at first
= 7 u - 9
= 7 x 4 - 9
= 28 - 9
= 19
Answer(s): 19
