PSLE Cindy had a box of silver marbles and green marbles in the ratio 13 : 7. She removed an equal number of silver marbles and green marbles from the box. The ratio of the number of silver marbles and green marbles left in the box became 7 : 2. What percentage of the marbles were left in the box?
|
Silver marbles |
Green marbles |
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 Cindy removed an equal number of silver marbles and green marbles, the difference between the number of silver marbles and green marbles at first and in the end remains the same.
LCM of 6 and 5 is 30.
Percentage of the marbles left in the box
=
54100 x 100%
= 2750 x 100%
= 54%
Answer: 54%