PSLE At first, a box contained 76 gold balls and some yellow beads. After some gold balls were removed,
57 of the balls were yellow. After 10 white balls were added to the box and now,
59 of the beads were yellow. What was the number of gold balls removed?
|
Yellow balls |
Gold balls |
White balls |
Total |
Before |
5 u |
76 |
0 |
|
Change 1 |
|
- ? |
|
+ ? |
After 1 |
5 u |
2 u |
0 |
7 u |
Change 2 |
|
|
+ 10 |
+ 2 u |
After 2 |
5 u |
2 u |
2 u |
9 u |
Some gold balls were removed at first. However, when 10 white balls were added, the number of gold balls remains unchanged.
Number of white balls added
= 9 u - 7 u
= 2 u
2 u = 10
1 u = 10 ÷ 2 = 5
Number of gold balls removed
= 76 - 2 u
= 76 - 2 x 5
= 76 - 10
= 66
Answer(s): 66