PSLE At first, a box contained 96 black marbles and some red beads. After some black marbles were removed,
35 of the marbles were red. After 60 green marbles were added to the box and now,
38 of the beads were red. What was the number of black marbles removed?
|
Red marbles |
Black marbles |
Green marbles |
Total |
Before |
3 u |
96 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
3 u |
2 u |
0 |
5 u |
Change 2 |
|
|
+ 60 |
+ 3 u |
After 2 |
3 u |
2 u |
3 u |
8 u |
Some black marbles were removed at first. However, when 60 green marbles were added, the number of black marbles remains unchanged.
Number of green marbles added
= 8 u - 5 u
= 3 u
3 u = 60
1 u = 60 ÷ 3 = 20
Number of black marbles removed
= 96 - 2 u
= 96 - 2 x 20
= 96 - 40
= 56
Answer(s): 56