PSLE Zoe had a bag of brown balls and white balls in the ratio 16 : 9. She removed an equal number of brown balls and white balls from the bag. The ratio of the number of brown balls and white balls left in the bag became 5 : 1. What percentage of the balls were left in the bag?
|
Brown balls |
White 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 Zoe removed an equal number of brown balls and white balls, the difference between the number of brown balls and white 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%