PSLE A box contained blue balls and grey balls. 70% of the balls were grey. After some yellow balls were added to the box, 49% of the balls were grey. What percentage of the balls in the box were yellow?
|
Grey |
Blue |
Yellow |
Total |
Before |
7 u |
3 u |
|
10 u |
Change |
|
|
+ ? |
|
After |
49% |
21% |
|
100% |
70% =
70100 =
710 The number of grey balls remains unchanged.
7 u → 49%
1 u → 49% ÷ 7 = 7%
3 u → 3 x 7 = 21%
Percentage of the balls in the box that were yellow
= 100% - 49% - 21%
= 30%
Answer(s): 30%