PSLE Raeann had a basket of grey balls and red balls in the ratio 17 : 9. She removed an equal number of grey balls and red balls from the basket. The ratio of the number of grey balls and red balls left in the basket became 9 : 4. What percentage of the balls were left in the basket?
|
Grey balls |
Red balls |
Difference |
Total |
Before |
17x5 = 85 u |
9x5 = 45 u |
8x5 = 40 u |
26x5 = 130 u |
Change |
- 13 u |
- 13 u |
|
|
After |
9x8 = 72 u |
4x8 = 32 u |
5x8 = 40 u |
13x8 = 104 u |
When Raeann removed an equal number of grey balls and red balls, the difference between the number of grey balls and red balls at first and in the end remains the same.
LCM of 8 and 5 is 40.
Percentage of the balls left in the basket
=
104130 x 100%
= 45 x 100%
= 80%
Answer: 80%