PSLE
Yen had a total of 248 green and black beads. She used 50 green beads and 10% of the black beads. After that, the ratio of the number of green beads to black beads Yen had was 8 : 9.

1. What fraction of her black beads did Yen use? Give your answer in the simplest form.
2. How many beads did Yen have in the end?

	Green beads	Black beads	Total
Before	8 u + 50	10 u	18 u + 50
Change	- 50	- 1 u
After	8 u	9 u	17 u
Comparing green beads and black beads in the end	8	9	17

(a)
10% = ¹⁰₁₀₀ = ¹₁₀

Fraction of her black beads that Yen used = ¹₁₀

(b)
The number of black 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 black beads at first = 10 u
Number of green beads at first = 8 u + 50

Total number of beads at first
= 10 u + 8 u + 50
= 18 u + 50

18 u + 50 = 248
18 u = 248 - 50
18 u = 198

1 u = 198 ÷ 18 = 11

Number of black beads in the end = 9 u
Number of green beads in the end = 8 u

Total number of beads in the end
= 8 u + 9 u
= 17 u
= 17 x 11
= 187

Answer(s): (a)¹₁₀; (b) 187