PSLE Jean had a box of red balls and grey balls in the ratio 13 : 9. She removed an equal number of red balls and grey balls from the box. The ratio of the number of red balls and grey balls left in the box became 8 : 3. What percentage of the balls were left in the box?
|
Red balls |
Grey balls |
Difference |
Total |
Before |
13x5 = 65 u |
9x5 = 45 u |
4x5 = 20 u |
22x5 = 110 u |
Change |
- 33 u |
- 33 u |
|
|
After |
8x4 = 32 u |
3x4 = 12 u |
5x4 = 20 u |
11x4 = 44 u |
When Jean removed an equal number of red balls and grey balls, the difference between the number of red balls and grey balls at first and in the end remains the same.
LCM of 4 and 5 is 20.
Percentage of the balls left in the box
=
44110 x 100%
= 25 x 100%
= 40%
Answer: 40%