PSLE Victoria had a box of silver balls and black balls in the ratio 17 : 8. She removed an equal number of silver balls and black balls from the box. The ratio of the number of silver balls and black balls left in the box became 5 : 1. What percentage of the balls were left in the box?
|
Silver balls |
Black balls |
Difference |
Total |
Before |
17x4 = 68 u |
8x4 = 32 u |
9x4 = 36 u |
25x4 = 100 u |
Change |
- 23 u |
- 23 u |
|
|
After |
5x9 = 45 u |
1x9 = 9 u |
4x9 = 36 u |
6x9 = 54 u |
When Victoria removed an equal number of silver balls and black balls, the difference between the number of silver balls and black balls at first and in the end remains the same.
LCM of 9 and 4 is 36.
Percentage of the balls left in the box
=
54100 x 100%
= 2750 x 100%
= 54%
Answer: 54%