PSLE
Emma bought some chocolate bars and gave half of it to Cody. Cody bought some lollipops and gave half of it to Emma. Emma ate 5 lollipops and Cody ate 8 chocolate bars. The ratio of Emma's lollipops to chocolate bars became 1 : 4 and the ratio of Cody's lollipops to chocolate bars became 1 : 2. How many chocolate bars did Emma buy?

	Emma		Cody
	Lollipops	Chocolate bars	Lollipops	Chocolate bars
Before	1 u + 5	4 u	1 p	2 p + 8
Change	- 5			- 8
After	1 u	4 u	1 p	2 p

After Emma gave half of the chocolate bars to Cody and Cody gave half of his lollipops to Emma, Cody and Emma had same number of lollipops and chocolate bars before each ate some.

4 u = 2 p + 8 
4 u - 8 = 2 p --- (1)

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

Make p the same.

(2)_x2
2 u + 10 = 2 p --- (3)

(1) = (3)
4 u - 8 = 2 u + 10 
4 u - 2 u = 10 + 8
2 u = 18

1 u = 18 ÷ 2 = 9

Number of chocolate bars that Emma bought
= 2 x 4 u
= 8 u
= 8 x 9
= 72

Answer(s): 72