PSLE Pamela had a bag of red balls and grey balls in the ratio 13 : 7. She removed an equal number of red balls and grey balls from the bag. The ratio of the number of red balls and grey balls left in the bag became 8 : 3. What percentage of the balls were left in the bag?
|
Red balls |
Grey balls |
Difference |
Total |
Before |
13x5 = 65 u |
7x5 = 35 u |
6x5 = 30 u |
20x5 = 100 u |
Change |
- 17 u |
- 17 u |
|
|
After |
8x6 = 48 u |
3x6 = 18 u |
5x6 = 30 u |
11x6 = 66 u |
When Pamela 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 6 and 5 is 30.
Percentage of the balls left in the bag
=
66100 x 100%
= 3350 x 100%
= 66%
Answer: 66%