PSLE
A box contained yellow and orange beads. At first, the number of yellow beads was ¹₅ the number of orange beads. After ¹₂ of the yellow beads and ¹₄ of the orange beads were used, 187 beads were left.

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

	Yellow	Orange
Comparing yellow beads and orange beads at first	1x4 = 4 u	5x4 = 20 u
Before	2x2 = 4 u	4x5 = 20 u
Change	- 1x2 =  - 2 u	- 1x5 = - 5 u
After	1x2 =  2 u	3x5 = 15 u

(a)
The number of orange beads at first is repeated. Make the number of orange beads at first the same. 
LCM of 5 and 4 is 20.

The number of yellow beads at first is repeated.

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

Fraction of the beads left
= ^{2 + 15}_{4 + 20} 
= ¹⁷₂₄

(b)
Number of beads left
= 2 u + 15 u
= 17 u

17 u = 187

1 u = 187 ÷ 17 = 11

Number of beads used
= 2 u + 5 u
= 7 u
= 7 x 11
= 77

Answer(s): (a) ¹⁷₂₄; (b) 77