PSLE A box contained blue balls and gold balls. 60% of the balls were gold. After some black balls were added to the box, 30% of the balls were gold. What percentage of the balls in the box were black?
|
Gold |
Blue |
Black |
Total |
Before |
3 u |
2 u |
|
5 u |
Change |
|
|
+ ? |
|
After |
30% |
20% |
|
100% |
60% =
60100 =
35 The number of gold balls remains unchanged.
3 u → 30%
1 u → 30% ÷ 3 = 10%
2 u → 2 x 10 = 20%
Percentage of the balls in the box that were black
= 100% - 30% - 20%
= 50%
Answer(s): 50%