PSLE A box contained yellow marbles and grey marbles. 30% of the marbles were grey. After some green marbles were added to the box, 18% of the marbles were grey. What percentage of the marbles in the box were green?
|
Grey |
Yellow |
Green |
Total |
Before |
3 u |
7 u |
|
10 u |
Change |
|
|
+ ? |
|
After |
18% |
42% |
|
100% |
30% =
30100 =
310 The number of grey marbles remains unchanged.
3 u → 18%
1 u → 18% ÷ 3 = 6%
7 u → 7 x 6 = 42%
Percentage of the marbles in the box that were green
= 100% - 18% - 42%
= 40%
Answer(s): 40%