PSLE Kimberly had a basket of yellow balls and black balls in the ratio 13 : 7. She removed an equal number of yellow balls and black balls from the basket. The ratio of the number of yellow balls and black balls left in the basket became 9 : 4. What percentage of the balls were left in the basket?
|
Yellow balls |
Black 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 Kimberly removed an equal number of yellow balls and black balls, the difference between the number of yellow balls and black 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%