PSLE A box contained blue balls and grey balls. 70% of the balls were grey. After some yellow balls were added to the box, 42% 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 |
42% |
18% |
|
100% |
70% =
70100 =
710 The number of grey balls remains unchanged.
7 u → 42%
1 u → 42% ÷ 7 = 6%
3 u → 3 x 6 = 18%
Percentage of the balls in the box that were yellow
= 100% - 42% - 18%
= 40%
Answer(s): 40%