Emily has a bag containing some orange and blue marbles. If she adds in 9 orange marbles, 20% of the marbles in the bag are blue. If she adds in another 20 blue marbles, 40% of the marbles in the bag are blue. How many orange marbles are in the bag?
| |
Orange marbles |
Blue marbles |
| Before |
12 u - 9 |
3 u |
| Change 1 |
+ 9 |
|
| After 1 |
4x3 =
12 u |
1x3 =
3 u |
| Change 2 |
|
+ 20 |
| After 2 |
3x4 =
12 u |
2x4 =
8 u |
20% =
20100 =
1540% =
40100 =
25The number of orange marbles remains unchanged at the second change when she adds in another 20 blue marbles. Make the number of orange marbles the same at the second change. LCM of 4 and 3 is 12.
Number of blue marbles added
= 8 u - 3 u
= 5 u
5 u = 20
1 u = 20 ÷ 5 = 4
Number of orange marbles at first
= 12 u - 9
= 12 x 4 - 9
= 48 - 9
= 39
Answer(s): 39
