PSLE Anna had a bag of white balls and yellow balls in the ratio 13 : 7. She removed an equal number of white balls and yellow balls from the bag. The ratio of the number of white balls and yellow balls left in the bag became 7 : 2. What percentage of the balls were left in the bag?
|
White balls |
Yellow balls |
Difference |
Total |
Before |
13x5 = 65 u |
7x5 = 35 u |
6x5 = 30 u |
20x5 = 100 u |
Change |
- 23 u |
- 23 u |
|
|
After |
7x6 = 42 u |
2x6 = 12 u |
5x6 = 30 u |
9x6 = 54 u |
When Anna removed an equal number of white balls and yellow balls, the difference between the number of white balls and yellow 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
=
54100 x 100%
= 2750 x 100%
= 54%
Answer: 54%