Gem has a bag containing some blue and silver buttons. If she adds in 9 blue buttons, 20% of the buttons in the bag are silver. If she adds in another 15 silver buttons, 60% of the buttons in the bag are silver. How many blue buttons are in the bag?
| |
Blue buttons |
Silver buttons |
| Before |
4 u - 9 |
1 u |
| Change 1 |
+ 9 |
|
| After 1 |
4x1 =
4 u |
1x1 =
1 u |
| Change 2 |
|
+ 15 |
| After 2 |
2x2 =
4 u |
3x2 =
6 u |
20% =
20100 =
1560% =
60100 =
35The number of blue buttons remains unchanged at the second change when she adds in another 15 silver buttons. Make the number of blue buttons the same at the second change. LCM of 4 and 2 is 4.
Number of silver buttons added
= 6 u - 1 u
= 5 u
5 u = 15
1 u = 15 ÷ 5 = 3
Number of blue buttons at first
= 4 u - 9
= 4 x 3 - 9
= 12 - 9
= 3
Answer(s): 3
