PSLE
Emily bought some jelly beans and gave half of it to Sean. Sean bought some chocolate bars and gave half of it to Emily. Emily ate 2 chocolate bars and Sean ate 23 jelly beans. The ratio of Emily's chocolate bars to jelly beans became 1 : 5 and the ratio of Sean's chocolate bars to jelly beans became 1 : 2. How many chocolate bars did Sean buy?

	Emily		Sean
	Chocolate bars	Jelly beans	Chocolate bars	Jelly beans
Before	1 u + 2	5 u	1 p	2 p + 23
Change	- 2			- 23
After	1 u	5 u	1 p	2 p

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

5 u = 2 p + 23 
5 u - 23 = 2 p --- (1)

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

Make p the same.

(2)_x2
2 u + 4 = 2 p --- (3)

(1) = (3)
5 u - 23 = 2 u + 4 
5 u - 2 u = 4 + 23
3 u = 27

1 u = 27 ÷ 3 = 9

1 p
= 1 u + 2
= 9 + 2
= 11

Number of chocolate bars that Sean bought
= 2 p
= 2 x 11
= 22

Answer(s): 22