PSLE A box contained purple balls and silver balls. 30% of the balls were silver. After some yellow balls were added to the box, 21% of the balls were silver. What percentage of the balls in the box were yellow?
|
Silver |
Purple |
Yellow |
Total |
Before |
3 u |
7 u |
|
10 u |
Change |
|
|
+ ? |
|
After |
21% |
49% |
|
100% |
30% =
30100 =
310 The number of silver balls remains unchanged.
3 u → 21%
1 u → 21% ÷ 3 = 7%
7 u → 7 x 7 = 49%
Percentage of the balls in the box that were yellow
= 100% - 21% - 49%
= 30%
Answer(s): 30%