PSLE Abi had a box of blue balls and brown balls in the ratio 17 : 7. She removed an equal number of blue balls and brown balls from the box. The ratio of the number of blue balls and brown balls left in the box became 7 : 2. What percentage of the balls were left in the box?
|
Blue balls |
Brown balls |
Difference |
Total |
Before |
17x1 = 17 u |
7x1 = 7 u |
10x1 = 10 u |
24x1 = 24 u |
Change |
- 3 u |
- 3 u |
|
|
After |
7x2 = 14 u |
2x2 = 4 u |
5x2 = 10 u |
9x2 = 18 u |
When Abi removed an equal number of blue balls and brown balls, the difference between the number of blue balls and brown balls at first and in the end remains the same.
LCM of 10 and 5 is 10.
Percentage of the balls left in the box
=
1824 x 100%
= 34 x 100%
= 75%
Answer: 75%