PSLE Gillian had a basket of white balls and gold balls in the ratio 13 : 7. She removed an equal number of white balls and gold balls from the basket. The ratio of the number of white balls and gold balls left in the basket became 9 : 4. What percentage of the balls were left in the basket?
|
White balls |
Gold balls |
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 Gillian removed an equal number of white balls and gold balls, the difference between the number of white balls and gold balls at first and in the end remains the same.
LCM of 6 and 5 is 30.
Percentage of the balls left in the basket
=
78100 x 100%
= 3950 x 100%
= 78%
Answer: 78%