PSLE At first, a box contained 60 silver balls and some gold beads. After some silver balls were removed,
58 of the balls were gold. After 72 yellow balls were added to the box and now,
512 of the beads were gold. What was the number of silver balls removed?
|
Gold balls |
Silver balls |
Yellow balls |
Total |
Before |
5 u |
60 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
5 u |
3 u |
0 |
8 u |
Change 2 |
|
|
+ 72 |
+ 4 u |
After 2 |
5 u |
3 u |
4 u |
12 u |
Some silver balls were removed at first. However, when 72 yellow balls were added, the number of silver balls remains unchanged.
Number of yellow balls added
= 12 u - 8 u
= 4 u
4 u = 72
1 u = 72 ÷ 4 = 18
Number of silver balls removed
= 60 - 3 u
= 60 - 3 x 18
= 60 - 54
= 6
Answer(s): 6