PSLE A box contained grey balls and black balls. 70% of the balls were black. After some purple balls were added to the box, 28% of the balls were black. What percentage of the balls in the box were purple?
|
Black |
Grey |
Purple |
Total |
Before |
7 u |
3 u |
|
10 u |
Change |
|
|
+ ? |
|
After |
28% |
12% |
|
100% |
70% =
70100 =
710 The number of black balls remains unchanged.
7 u → 28%
1 u → 28% ÷ 7 = 4%
3 u → 3 x 4 = 12%
Percentage of the balls in the box that were purple
= 100% - 28% - 12%
= 60%
Answer(s): 60%