PSLE Tina had a box of yellow balls and silver balls in the ratio 13 : 7. She removed an equal number of yellow balls and silver balls from the box. The ratio of the number of yellow balls and silver balls left in the box became 7 : 2. What percentage of the balls were left in the box?
|
Yellow balls |
Silver balls |
Difference |
Total |
Before |
13x5 = 65 u |
7x5 = 35 u |
6x5 = 30 u |
20x5 = 100 u |
Change |
- 23 u |
- 23 u |
|
|
After |
7x6 = 42 u |
2x6 = 12 u |
5x6 = 30 u |
9x6 = 54 u |
When Tina removed an equal number of yellow balls and silver balls, the difference between the number of yellow balls and silver balls at first and in the end remains the same.
LCM of 6 and 5 is 30.
Percentage of the balls left in the box
=
54100 x 100%
= 2750 x 100%
= 54%
Answer: 54%