PSLE Joelle had a bag of black beads and gold beads in the ratio 16 : 9. She removed an equal number of black beads and gold beads from the bag. The ratio of the number of black beads and gold beads left in the bag became 7 : 3. What percentage of the beads were left in the bag?
|
Black beads |
Gold beads |
Difference |
Total |
Before |
16x4 = 64 u |
9x4 = 36 u |
7x4 = 28 u |
25x4 = 100 u |
Change |
- 15 u |
- 15 u |
|
|
After |
7x7 = 49 u |
3x7 = 21 u |
4x7 = 28 u |
10x7 = 70 u |
When Joelle removed an equal number of black beads and gold beads, the difference between the number of black beads and gold beads at first and in the end remains the same.
LCM of 7 and 4 is 28.
Percentage of the beads left in the bag
=
70100 x 100%
= 710 x 100%
= 70%
Answer: 70%