Mary has a bag containing some pink and red coins. If she adds in 6 pink coins, 25% of the coins in the bag are red. If she adds in another 6 red coins, 30% of the coins in the bag are red. How many pink coins are in the bag?
| |
Pink coins |
Red coins |
| Before |
21 u - 6 |
7 u |
| Change 1 |
+ 6 |
|
| After 1 |
3x7 =
21 u |
1x7 =
7 u |
| Change 2 |
|
+ 6 |
| After 2 |
7x3 =
21 u |
3x3 =
9 u |
25% =
25100 =
1430% =
30100 =
310The number of pink coins remains unchanged at the second change when she adds in another 6 red coins. Make the number of pink coins the same at the second change. LCM of 3 and 7 is 21.
Number of red coins added
= 9 u - 7 u
= 2 u
2 u = 6
1 u = 6 ÷ 2 = 3
Number of pink coins at first
= 21 u - 6
= 21 x 3 - 6
= 63 - 6
= 57
Answer(s): 57
