PSLE
Nicole bought some lollipops and gave half of it to Tommy. Tommy bought some chocolate bars and gave half of it to Nicole. Nicole ate 4 chocolate bars and Tommy ate 4 lollipops. The ratio of Nicole's chocolate bars to lollipops became 1 : 6 and the ratio of Tommy's chocolate bars to lollipops became 1 : 4. How many chocolate bars did Tommy buy?

	Nicole		Tommy
	Chocolate bars	Lollipops	Chocolate bars	Lollipops
Before	1 u + 4	6 u	1 p	4 p + 4
Change	- 4			- 4
After	1 u	6 u	1 p	4 p

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

6 u = 4 p + 4 
6 u - 4 = 4 p --- (1)

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

Make p the same.

(2)_x4
4 u + 16 = 4 p --- (3)

(1) = (3)
6 u - 4 = 4 u + 16 
6 u - 4 u = 16 + 4
2 u = 20

1 u = 20 ÷ 2 = 10

1 p
= 1 u + 4
= 10 + 4
= 14

Number of chocolate bars that Tommy bought
= 2 p
= 2 x 14
= 28

Answer(s): 28