PSLE Penelope had a box of brown marbles and silver marbles in the ratio 17 : 7. She removed an equal number of brown marbles and silver marbles from the box. The ratio of the number of brown marbles and silver marbles left in the box became 7 : 2. What percentage of the marbles were left in the box?
|
Brown marbles |
Silver marbles |
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 Penelope removed an equal number of brown marbles and silver marbles, the difference between the number of brown marbles and silver marbles at first and in the end remains the same.
LCM of 10 and 5 is 10.
Percentage of the marbles left in the box
=
1824 x 100%
= 34 x 100%
= 75%
Answer: 75%