PSLE
Diana bought some chocolate bars and gave half of it to Eric. Eric bought some jelly beans and gave half of it to Diana. Diana ate 5 jelly beans and Eric ate 4 chocolate bars. The ratio of Diana's jelly beans to chocolate bars became 1 : 4 and the ratio of Eric's jelly beans to chocolate bars became 1 : 2. How many jelly beans did Eric buy?

	Diana		Eric
	Jelly beans	Chocolate bars	Jelly beans	Chocolate bars
Before	1 u + 5	4 u	1 p	2 p + 4
Change	- 5			- 4
After	1 u	4 u	1 p	2 p

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

4 u = 2 p + 4 
4 u - 4 = 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 - 4 = 2 u + 10 
4 u - 2 u = 10 + 4
2 u = 14

1 u = 14 ÷ 2 = 7

1 p
= 1 u + 5
= 7 + 5
= 12

Number of jelly beans that Eric bought
= 2 p
= 2 x 12
= 24

Answer(s): 24