PSLE Tina had a box of purple balls and brown balls in the ratio 17 : 8. She removed an equal number of purple balls and brown balls from the box. The ratio of the number of purple balls and brown balls left in the box became 7 : 3. What percentage of the balls were left in the box?
|
Purple balls |
Brown balls |
Difference |
Total |
Before |
17x4 = 68 u |
8x4 = 32 u |
9x4 = 36 u |
25x4 = 100 u |
Change |
- 5 u |
- 5 u |
|
|
After |
7x9 = 63 u |
3x9 = 27 u |
4x9 = 36 u |
10x9 = 90 u |
When Tina removed an equal number of purple balls and brown balls, the difference between the number of purple balls and brown 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
=
90100 x 100%
= 910 x 100%
= 90%
Answer: 90%