PSLE Tiffany had a basket of blue balls and grey balls in the ratio 13 : 7. She removed an equal number of blue balls and grey balls from the basket. The ratio of the number of blue balls and grey balls left in the basket became 5 : 2. What percentage of the balls were left in the basket?
|
Blue balls |
Grey balls |
Difference |
Total |
Before |
13x1 = 13 u |
7x1 = 7 u |
6x1 = 6 u |
20x1 = 20 u |
Change |
- 3 u |
- 3 u |
|
|
After |
5x2 = 10 u |
2x2 = 4 u |
3x2 = 6 u |
7x2 = 14 u |
When Tiffany removed an equal number of blue balls and grey balls, the difference between the number of blue balls and grey balls at first and in the end remains the same.
LCM of 6 and 3 is 6.
Percentage of the balls left in the basket
=
1420 x 100%
= 710 x 100%
= 70%
Answer: 70%