PSLE At first, a box contained 91 red beads and some grey beads. After some red beads were removed,
37 of the beads were grey. After 76 white beads were added to the box and now,
311 of the beads were grey. What was the number of red beads removed?
|
Grey beads |
Red beads |
White beads |
Total |
Before |
3 u |
91 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
3 u |
4 u |
0 |
7 u |
Change 2 |
|
|
+ 76 |
+ 4 u |
After 2 |
3 u |
4 u |
4 u |
11 u |
Some red beads were removed at first. However, when 76 white beads were added, the number of red beads remains unchanged.
Number of white beads added
= 11 u - 7 u
= 4 u
4 u = 76
1 u = 76 ÷ 4 = 19
Number of red beads removed
= 91 - 4 u
= 91 - 4 x 19
= 91 - 76
= 15
Answer(s): 15