PSLE
Dana bought some chocolate bars and gave half of it to Nick. Nick bought some sweets and gave half of it to Dana. Dana ate 2 sweets and Nick ate 39 chocolate bars. The ratio of Dana's sweets to chocolate bars became 1 : 6 and the ratio of Nick's sweets to chocolate bars became 1 : 3. How many sweets did Nick buy?

	Dana		Nick
	Sweets	Chocolate bars	Sweets	Chocolate bars
Before	1 u + 2	6 u	1 p	3 p + 39
Change	- 2			- 39
After	1 u	6 u	1 p	3 p

After Dana gave half of the chocolate bars to Nick and Nick gave half of his sweets to Dana, Nick and Dana had same number of sweets and chocolate bars before each ate some.

6 u = 3 p + 39 
6 u - 39 = 3 p --- (1)

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

Make p the same.

(2)_x3
3 u + 6 = 3 p --- (3)

(1) = (3)
6 u - 39 = 3 u + 6 
6 u - 3 u = 6 + 39
3 u = 45

1 u = 45 ÷ 3 = 15

1 p
= 1 u + 2
= 15 + 2
= 17

Number of sweets that Nick bought
= 2 p
= 2 x 17
= 34

Answer(s): 34