PSLE At first, a box contained 65 brown marbles and some gold beads. After some brown marbles were removed,
25 of the marbles were gold. After 40 green marbles were added to the box and now,
27 of the beads were gold. What was the number of brown marbles removed?
|
Gold marbles |
Brown marbles |
Green marbles |
Total |
Before |
2 u |
65 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
2 u |
3 u |
0 |
5 u |
Change 2 |
|
|
+ 40 |
+ 2 u |
After 2 |
2 u |
3 u |
2 u |
7 u |
Some brown marbles were removed at first. However, when 40 green marbles were added, the number of brown marbles remains unchanged.
Number of green marbles added
= 7 u - 5 u
= 2 u
2 u = 40
1 u = 40 ÷ 2 = 20
Number of brown marbles removed
= 65 - 3 u
= 65 - 3 x 20
= 65 - 60
= 5
Answer(s): 5