PSLE A box contained red balls and green balls. 40% of the balls were green. After some black balls were added to the box, 22% of the balls were green. What percentage of the balls in the box were black?
|
Green |
Red |
Black |
Total |
Before |
2 u |
3 u |
|
5 u |
Change |
|
|
+ ? |
|
After |
22% |
33% |
|
100% |
40% =
40100 =
25 The number of green balls remains unchanged.
2 u → 22%
1 u → 22% ÷ 2 = 11%
3 u → 3 x 11 = 33%
Percentage of the balls in the box that were black
= 100% - 22% - 33%
= 45%
Answer(s): 45%