PSLE Tammy had a bag of silver balls and purple balls in the ratio 18 : 7. She removed an equal number of silver balls and purple balls from the bag. The ratio of the number of silver balls and purple balls left in the bag became 5 : 1. What percentage of the balls were left in the bag?
|
Silver balls |
Purple balls |
Difference |
Total |
Before |
18x4 = 72 u |
7x4 = 28 u |
11x4 = 44 u |
25x4 = 100 u |
Change |
- 17 u |
- 17 u |
|
|
After |
5x11 = 55 u |
1x11 = 11 u |
4x11 = 44 u |
6x11 = 66 u |
When Tammy removed an equal number of silver balls and purple balls, the difference between the number of silver balls and purple balls at first and in the end remains the same.
LCM of 11 and 4 is 44.
Percentage of the balls left in the bag
=
66100 x 100%
= 3350 x 100%
= 66%
Answer: 66%