PSLE
Xylia bought some chocolate bars and gave half of it to Ken. Ken bought some jelly beans and gave half of it to Xylia. Xylia ate 4 jelly beans and Ken ate 8 chocolate bars. The ratio of Xylia's jelly beans to chocolate bars became 1 : 5 and the ratio of Ken's jelly beans to chocolate bars became 1 : 3. How many chocolate bars did Xylia buy?

	Xylia		Ken
	Jelly beans	Chocolate bars	Jelly beans	Chocolate bars
Before	1 u + 4	5 u	1 p	3 p + 8
Change	- 4			- 8
After	1 u	5 u	1 p	3 p

After Xylia gave half of the chocolate bars to Ken and Ken gave half of his jelly beans to Xylia, Ken and Xylia had same number of jelly beans and chocolate bars before each ate some.

5 u = 3 p + 8 
5 u - 8 = 3 p --- (1)

1 u + 4 = 1 p --- (2)

Make p the same.

(2)_x3
3 u + 12 = 3 p --- (3)

(1) = (3)
5 u - 8 = 3 u + 12 
5 u - 3 u = 12 + 8
2 u = 20

1 u = 20 ÷ 2 = 10

Number of chocolate bars that Xylia bought
= 2 x 5 u
= 10 u
= 10 x 10
= 100

Answer(s): 100