PSLE At first, a box contained 71 grey marbles and some pink beads. After some grey marbles were removed,
57 of the marbles were pink. After 55 white marbles were added to the box and now,
512 of the beads were pink. What was the number of grey marbles removed?
|
Pink marbles |
Grey marbles |
White marbles |
Total |
Before |
5 u |
71 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
5 u |
2 u |
0 |
7 u |
Change 2 |
|
|
+ 55 |
+ 5 u |
After 2 |
5 u |
2 u |
5 u |
12 u |
Some grey marbles were removed at first. However, when 55 white marbles were added, the number of grey marbles remains unchanged.
Number of white marbles added
= 12 u - 7 u
= 5 u
5 u = 55
1 u = 55 ÷ 5 = 11
Number of grey marbles removed
= 71 - 2 u
= 71 - 2 x 11
= 71 - 22
= 49
Answer(s): 49