PSLE
Shannon bought some lollipops and gave half of it to Jeremy. Jeremy bought some chocolate bars and gave half of it to Shannon. Shannon ate 7 chocolate bars and Jeremy ate 15 lollipops. The ratio of Shannon's chocolate bars to lollipops became 1 : 6 and the ratio of Jeremy's chocolate bars to lollipops became 1 : 3. How many lollipops did Shannon buy?

	Shannon		Jeremy
	Chocolate bars	Lollipops	Chocolate bars	Lollipops
Before	1 u + 7	6 u	1 p	3 p + 15
Change	- 7			- 15
After	1 u	6 u	1 p	3 p

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

6 u = 3 p + 15 
6 u - 15 = 3 p --- (1)

1 u + 7 = 1 p --- (2)

Make p the same.

(2)_x3
3 u + 21 = 3 p --- (3)

(1) = (3)
6 u - 15 = 3 u + 21 
6 u - 3 u = 21 + 15
3 u = 36

1 u = 36 ÷ 3 = 12

Number of lollipops that Shannon bought
= 2 x 6 u
= 12 u
= 12 x 12
= 144

Answer(s): 144