PSLE A box contained red balls and black balls. 40% of the balls were black. After some yellow balls were added to the box, 32% of the balls were black. What percentage of the balls in the box were yellow?
|
Black |
Red |
Yellow |
Total |
Before |
2 u |
3 u |
|
5 u |
Change |
|
|
+ ? |
|
After |
32% |
48% |
|
100% |
40% =
40100 =
25 The number of black balls remains unchanged.
2 u → 32%
1 u → 32% ÷ 2 = 16%
3 u → 3 x 16 = 48%
Percentage of the balls in the box that were yellow
= 100% - 32% - 48%
= 20%
Answer(s): 20%