PSLE Xylia had a basket of silver balls and blue balls in the ratio 16 : 9. She removed an equal number of silver balls and blue balls from the basket. The ratio of the number of silver balls and blue balls left in the basket became 7 : 3. What percentage of the balls were left in the basket?
|
Silver balls |
Blue balls |
Difference |
Total |
Before |
16x4 = 64 u |
9x4 = 36 u |
7x4 = 28 u |
25x4 = 100 u |
Change |
- 15 u |
- 15 u |
|
|
After |
7x7 = 49 u |
3x7 = 21 u |
4x7 = 28 u |
10x7 = 70 u |
When Xylia 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 basket
=
70100 x 100%
= 710 x 100%
= 70%
Answer: 70%