I am bored... I got no place to go and nothing to do since my sister is having her PSLE... I think some ppl might heard the complains about this year PSLE Math Paper. It is really hard I guess. This is one qns I got from the yahoo news.

"Jim bought some chocolates and gave half of it to Ken. Ken bought some sweets and gave half of it to Jim. Jim ate 12 sweets and Ken ate 18 chocolates. The ratio of Jim’s sweets to chocolates became 1:7 and the ratio of Ken’s sweets to chocolates became 1:4. How many sweets did Ken buy?"

Let x be the number of sweets ken bought.
Let y be the number of chocolate Kim bought.

1:7 is 1/2x - 12(sweets eaten) : 1/2y
1:4 is 1/2x : 1/2y - 18(chocolate eaten)

To form 2 equation. (DIFFICULT PART)
Must make 1/2y become 1/14y by dividing by 7. (1:7) and
(1/2y - 18) become (1/8y - 4.5) by dividing by 4. (1:4)

1st Equation --> 1/2x - 12 = 1/14y
2nd Equation --> 1/2x = 1/8y - 4.5

Then SUB 2nd Equation into the 1st Equation
1/8y - 4.5 - 12 = 1/14y
y = 308 chocolates

Then choose any equation to put y into it. For me I use the 2nd Equation.
1/2x = [(1/8)*308]- 4.5
x = 68

The ANS: 68. This qns is hard but solve-able leh.. The thing it is hard is the ratio part making the algebra more confusing. I think the students were not taught so much on algebra and the difficult part is on forming the 2 equation. I formed the wrong equation at first too. I forget to divide by 4 or mutiply by 4. Because ratio does not mean =. 1:4 does not mean 1 = 4. And I think it is difficult for them to use "x" and "y". They had not learnt simultaneous equations i guess???