Shannon has a bag containing some black and blue stickers. If she adds in 7 black stickers, 10% of the stickers in the bag are blue. If she adds in another 30 blue stickers, 40% of the stickers in the bag are blue. How many black stickers are in the bag?
| |
Black stickers |
Blue stickers |
| Before |
9 u - 7 |
1 u |
| Change 1 |
+ 7 |
|
| After 1 |
9x1 =
9 u |
1x1 =
1 u |
| Change 2 |
|
+ 30 |
| After 2 |
3x3 =
9 u |
2x3 =
6 u |
10% =
10100 =
11040% =
40100 =
25The number of black stickers remains unchanged at the second change when she adds in another 30 blue stickers. Make the number of black stickers the same at the second change. LCM of 9 and 3 is 9.
Number of blue stickers added
= 6 u - 1 u
= 5 u
5 u = 30
1 u = 30 ÷ 5 = 6
Number of black stickers at first
= 9 u - 7
= 9 x 6 - 7
= 54 - 7
= 47
Answer(s): 47
