PSLE Cindy had a bag of silver balls and blue balls in the ratio 16 : 9. She removed an equal number of silver balls and blue balls from the bag. The ratio of the number of silver balls and blue balls left in the bag became 5 : 1. What percentage of the balls were left in the bag?
|
Silver balls |
Blue balls |
Difference |
Total |
Before |
16x4 = 64 u |
9x4 = 36 u |
7x4 = 28 u |
25x4 = 100 u |
Change |
- 29 u |
- 29 u |
|
|
After |
5x7 = 35 u |
1x7 = 7 u |
4x7 = 28 u |
6x7 = 42 u |
When Cindy removed an equal number of silver balls and blue balls, the difference between the number of silver balls and blue balls at first and in the end remains the same.
LCM of 7 and 4 is 28.
Percentage of the balls left in the bag
=
42100 x 100%
= 2150 x 100%
= 42%
Answer: 42%