PSLE A box contained yellow marbles and black marbles. 60% of the marbles were black. After some white marbles were added to the box, 21% of the marbles were black. What percentage of the marbles in the box were white?
|
Black |
Yellow |
White |
Total |
Before |
3 u |
2 u |
|
5 u |
Change |
|
|
+ ? |
|
After |
21% |
14% |
|
100% |
60% =
60100 =
35 The number of black marbles remains unchanged.
3 u → 21%
1 u → 21% ÷ 3 = 7%
2 u → 2 x 7 = 14%
Percentage of the marbles in the box that were white
= 100% - 21% - 14%
= 65%
Answer(s): 65%