PSLE At first, a container contained 74 blue balls and some white beads. After some blue balls were removed,
710 of the balls were white. After 18 black balls were added to the container and now,
713 of the beads were white. What was the number of blue balls removed?
|
White balls |
Blue balls |
Black balls |
Total |
Before |
7 u |
74 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
7 u |
3 u |
0 |
10 u |
Change 2 |
|
|
+ 18 |
+ 3 u |
After 2 |
7 u |
3 u |
3 u |
13 u |
Some blue balls were removed at first. However, when 18 black balls were added, the number of blue balls remains unchanged.
Number of black balls added
= 13 u - 10 u
= 3 u
3 u = 18
1 u = 18 ÷ 3 = 6
Number of blue balls removed
= 74 - 3 u
= 74 - 3 x 6
= 74 - 18
= 56
Answer(s): 56