PSLE Xandra had a total of 147 black and silver beads. She used 21 black beads and 80% of the silver beads. After that, the ratio of the number of black beads to silver beads Xandra had was 9 : 1.
- What fraction of her silver beads did Xandra use? Give your answer in the simplest form.
- How many beads did Xandra have in the end?
|
Black beads |
Silver beads |
Total |
Before |
9 u + 21 |
5 u |
14 u + 21 |
Change |
- 21 |
- 4 u |
|
After |
9 u |
1 u |
10 u |
Comparing black beads and silver beads in the end |
9 |
1 |
10 |
(a)
80% =
80100 =
45 Fraction of her silver beads that Xandra used =
45 (b)
The number of silver beads in the end is repeated.
Since the numbers are already the same, we do not need to use LCM to make them the same.
Number of silver beads at first = 5 u
Number of black beads at first = 9 u + 21
Total number of beads at first
= 5 u + 9 u + 21
= 14 u + 21
14 u + 21 = 147
14 u = 147 - 21
14 u = 126
1 u = 126 ÷ 14 = 9
Number of silver beads in the end = 1 u
Number of black beads in the end = 9 u
Total number of beads in the end
= 9 u + 1 u
= 10 u
= 10 x 9
= 90
Answer(s): (a)
45; (b) 90