Lynn has a bag containing some orange and black marbles. If she removes 15 orange marbles, 30% of the marbles in the bag are black. If she adds another 180 black marbles, 60% of the marbles in the bag are black. How many orange marbles are in the bag?
| |
Orange marbles |
Black marbles |
| Before |
14 u + 15 |
6 u |
| Change 1 |
- 15 |
|
| After 1 |
7x2 =
14 u |
3x2 =
6 u |
| Change 2 |
|
+ 180 |
| After 2 |
2x7 =
14 u |
3x7 =
21 u |
30% =
30100 =
31060% =
60100 =
35The number of orange marbles remains unchanged at the second change when she adds another 180 black marbles. Make the number of orange marbles the same at the second change. LCM of 7 and 2 is 14.
Number of black marbles added
= 21 u - 6 u
= 15 u
15 u = 180
1 u = 180 ÷ 15 = 12
Number of orange marbles at first
= 14 u + 15
= 14 x 12 + 15
= 168 + 15
= 183
Answer(s): 183
