PSLE
A box contained purple and green beads. At first, the number of purple beads was ¹₃ the number of green beads. After ¹₂ of the purple beads and ⁵₁₂ of the green beads were used, 54 beads were left.

1. What fraction of the beads were left? Leave your answer in the simplest form.
2. How many beads were used?

	Purple	Green
Comparing purple beads and green beads at first	1x4 = 4 u	3x4 = 12 u
Before	2x2 = 4 u	12x1 = 12 u
Change	- 1x2 =  - 2 u	- 5x1 = - 5 u
After	1x2 =  2 u	7x1 = 7 u

(a)
The number of green beads at first is repeated. Make the number of green beads at first the same. 
LCM of 3 and 12 is 12.

The number of purple beads at first is repeated.

Since the number of purple beads at first is 4 u, we make the total number of purple beads at first the same by multiplying 2 by 2 to become 4 u too.

Fraction of the beads left
= ^{2 + 7}_{4 + 12} 
= ⁹₁₆

(b)
Number of beads left
= 2 u + 7 u
= 9 u

9 u = 54

1 u = 54 ÷ 9 = 6

Number of beads used
= 2 u + 5 u
= 7 u
= 7 x 6
= 42

Answer(s): (a) ⁹₁₆; (b) 42