PSLE At first, a box contained 99 red balls and some blue beads. After some red balls were removed,
57 of the balls were blue. After 55 pink balls were added to the box and now,
512 of the beads were blue. What was the number of red balls removed?
|
Blue balls |
Red balls |
Pink balls |
Total |
Before |
5 u |
99 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
5 u |
2 u |
0 |
7 u |
Change 2 |
|
|
+ 55 |
+ 5 u |
After 2 |
5 u |
2 u |
5 u |
12 u |
Some red balls were removed at first. However, when 55 pink balls were added, the number of red balls remains unchanged.
Number of pink balls added
= 12 u - 7 u
= 5 u
5 u = 55
1 u = 55 ÷ 5 = 11
Number of red balls removed
= 99 - 2 u
= 99 - 2 x 11
= 99 - 22
= 77
Answer(s): 77