Yoko has a bag containing some pink and black buttons. If she removes 12 pink buttons, 30% of the buttons in the bag are black. If she adds another 105 black buttons, 60% of the buttons in the bag are black. How many pink buttons are in the bag?
| |
Pink buttons |
Black buttons |
| Before |
14 u + 12 |
6 u |
| Change 1 |
- 12 |
|
| After 1 |
7x2 =
14 u |
3x2 =
6 u |
| Change 2 |
|
+ 105 |
| After 2 |
2x7 =
14 u |
3x7 =
21 u |
30% =
30100 =
31060% =
60100 =
35The number of pink buttons remains unchanged at the second change when she adds another 105 black buttons. Make the number of pink buttons the same at the second change. LCM of 7 and 2 is 14.
Number of black buttons added
= 21 u - 6 u
= 15 u
15 u = 105
1 u = 105 ÷ 15 = 7
Number of pink buttons at first
= 14 u + 12
= 14 x 7 + 12
= 98 + 12
= 110
Answer(s): 110
