PSLE Kylie had a bag of white marbles and brown marbles in the ratio 13 : 7. She removed an equal number of white marbles and brown marbles from the bag. The ratio of the number of white marbles and brown marbles left in the bag became 9 : 4. What percentage of the marbles were left in the bag?
|
White marbles |
Brown marbles |
Difference |
Total |
Before |
13x5 = 65 u |
7x5 = 35 u |
6x5 = 30 u |
20x5 = 100 u |
Change |
- 11 u |
- 11 u |
|
|
After |
9x6 = 54 u |
4x6 = 24 u |
5x6 = 30 u |
13x6 = 78 u |
When Kylie removed an equal number of white marbles and brown marbles, the difference between the number of white marbles and brown marbles at first and in the end remains the same.
LCM of 6 and 5 is 30.
Percentage of the marbles left in the bag
=
78100 x 100%
= 3950 x 100%
= 78%
Answer: 78%