PSLE At first, a box contained 60 black marbles and some purple beads. After some black marbles were removed,
58 of the marbles were purple. After 84 red marbles were added to the box and now,
514 of the beads were purple. What was the number of black marbles removed?
|
Purple marbles |
Black marbles |
Red marbles |
Total |
Before |
5 u |
60 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
5 u |
3 u |
0 |
8 u |
Change 2 |
|
|
+ 84 |
+ 6 u |
After 2 |
5 u |
3 u |
6 u |
14 u |
Some black marbles were removed at first. However, when 84 red marbles were added, the number of black marbles remains unchanged.
Number of red marbles added
= 14 u - 8 u
= 6 u
6 u = 84
1 u = 84 ÷ 6 = 14
Number of black marbles removed
= 60 - 3 u
= 60 - 3 x 14
= 60 - 42
= 18
Answer(s): 18