PSLE
Cindy bought some jelly beans and gave half of it to Tom. Tom bought some lollipops and gave half of it to Cindy. Cindy ate 2 lollipops and Tom ate 12 jelly beans. The ratio of Cindy's lollipops to jelly beans became 1 : 4 and the ratio of Tom's lollipops to jelly beans became 1 : 2. How many lollipops did Tom buy?

	Cindy		Tom
	Lollipops	Jelly beans	Lollipops	Jelly beans
Before	1 u + 2	4 u	1 p	2 p + 12
Change	- 2			- 12
After	1 u	4 u	1 p	2 p

After Cindy gave half of the jelly beans to Tom and Tom gave half of his lollipops to Cindy, Tom and Cindy had same number of lollipops and jelly beans before each ate some.

4 u = 2 p + 12 
4 u - 12 = 2 p --- (1)

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

Make p the same.

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

(1) = (3)
4 u - 12 = 2 u + 4 
4 u - 2 u = 4 + 12
2 u = 16

1 u = 16 ÷ 2 = 8

1 p
= 1 u + 2
= 8 + 2
= 10

Number of lollipops that Tom bought
= 2 p
= 2 x 10
= 20

Answer(s): 20