PSLE
At first, a box contained 4 brown marbles and some purple beads. After some brown marbles were added, 57 of the marbles were purple. After 36 black marbles were added to the box and now, 59 of the beads were purple. What was the number of brown marbles added?
|
Purple marbles |
Brown marbles |
Black marbles |
Total |
Before |
5 u |
4 |
0 |
|
Change 1 |
|
+ ? |
|
+ ? |
After 1 |
5 u |
2 u |
0 |
7 u |
Change 2 |
|
|
+ 36 |
+ 2 u |
After 2 |
5 u |
2 u |
2 u |
9 u |
Some brown marbles were added at first. However, when 36 black marbles were added, the number of brown marbles remains unchanged.
Number of black marbles added
= 9 u - 7 u
= 2 u
2 u = 36
1 u = 36 ÷ 2 = 18
Number of brown marbles added
= 2 u - 4
= 2 x 18 - 4
= 36 - 4
= 32
Answer(s): 32