PSLE Min had a box of blue balls and purple balls in the ratio 13 : 7. She removed an equal number of blue balls and purple balls from the box. The ratio of the number of blue balls and purple balls left in the box became 4 : 1. What percentage of the balls were left in the box?
|
Blue balls |
Purple balls |
Difference |
Total |
Before |
13x1 = 13 u |
7x1 = 7 u |
6x1 = 6 u |
20x1 = 20 u |
Change |
- 5 u |
- 5 u |
|
|
After |
4x2 = 8 u |
1x2 = 2 u |
3x2 = 6 u |
5x2 = 10 u |
When Min removed an equal number of blue balls and purple balls, the difference between the number of blue balls and purple balls at first and in the end remains the same.
LCM of 6 and 3 is 6.
Percentage of the balls left in the box
=
1020 x 100%
= 12 x 100%
= 50%
Answer: 50%