PSLE At first, a box contained 70 green marbles and some gold beads. After some green marbles were removed,
35 of the marbles were gold. After 20 brown marbles were added to the box and now,
37 of the beads were gold. What was the number of green marbles removed?
|
Gold marbles |
Green marbles |
Brown marbles |
Total |
Before |
3 u |
70 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
3 u |
2 u |
0 |
5 u |
Change 2 |
|
|
+ 20 |
+ 2 u |
After 2 |
3 u |
2 u |
2 u |
7 u |
Some green marbles were removed at first. However, when 20 brown marbles were added, the number of green marbles remains unchanged.
Number of brown marbles added
= 7 u - 5 u
= 2 u
2 u = 20
1 u = 20 ÷ 2 = 10
Number of green marbles removed
= 70 - 2 u
= 70 - 2 x 10
= 70 - 20
= 50
Answer(s): 50