PSLE Zoe had a bag of black balls and pink balls in the ratio 18 : 7. She removed an equal number of black balls and pink balls from the bag. The ratio of the number of black balls and pink balls left in the bag became 9 : 1. What percentage of the balls were left in the bag?
|
Black balls |
Pink balls |
Difference |
Total |
Before |
18x8 = 144 u |
7x8 = 56 u |
11x8 = 88 u |
25x8 = 200 u |
Change |
- 45 u |
- 45 u |
|
|
After |
9x11 = 99 u |
1x11 = 11 u |
8x11 = 88 u |
10x11 = 110 u |
When Zoe removed an equal number of black balls and pink balls, the difference between the number of black balls and pink balls at first and in the end remains the same.
LCM of 11 and 8 is 88.
Percentage of the balls left in the bag
=
110200 x 100%
= 1120 x 100%
= 55%
Answer: 55%