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Tricky Questions

Posted: Fri Sep 02, 2011 9:14 pm
by ReplayMum
Can somebody help us solve these questions?
1. Sharpay is going shopping for some new stationery.
She can buy 3 pencils and 1 ruler for 50p, or 2 pencils and 2 rulers for 56p.
How much does each pencil cost?

2. In a magic square, the total for each row, column and diagnol is the same.
What is the value of m?
(sorry, I cannot draw the magic square, but I am sure you guys will get the idea)

? 4 17
? ? m
5 ? ?

I would very much appreciate if someone can assist in solving these questions.

Re: Tricky Questions

Posted: Fri Sep 02, 2011 10:33 pm
by no_ball
3pencils and 1ruler costs 50p
6 pencil and 2 ruler costs 100p

2pencil and 2ruler costs 56p

So 4 pencil costs 44 p (subtracting the 2 lines)
So 1 pencil costs 11p

Re: Tricky Questions

Posted: Fri Sep 02, 2011 10:51 pm
by Guest55
Errr - that's a bit complicated.

3 pencils and 1 ruler for 50p
2 pencils and 2 rulers for 56p, so easier to say that 1 pencil and 1 ruler is 28p.

This means the extra 2 pencils cost 22p ie 11p each..

Re: Tricky Questions

Posted: Fri Sep 02, 2011 11:04 pm
by no_ball
That's a bit illogical alright.

In my method the ruler is eliminated and only left with pencil. You. Your method does not explain the leap if faith.

Re: Tricky Questions

Posted: Sat Sep 03, 2011 8:56 am
by hermanmunster
hmm .. I would do it G55's way, there are often questions around where it comes down to an amount for a basic unit eg 1 apple + 1 orange + 1 raspeberry and all other answers come from there.

Re: Tricky Questions

Posted: Sat Sep 03, 2011 10:02 am
by no_ball
There are several factors to consider here..child's ability, time pressure, etc..

It's a case of horses for courses, as long as the principle is grasped and repeated successfully, then getting the right answer is the main consideration.

Re: Tricky Questions

Posted: Sat Sep 03, 2011 11:27 am
by Guest55
Your method is much longer - I have 'subtracted' the rulers because there are the same number in each sentence.

As a teacher I recommend to 'keep it simple' ... :D

Re: Tricky Questions

Posted: Sat Sep 03, 2011 12:19 pm
by ReplayMum
Thank you so much. I hope I can explain this to my DD properly though.

Anybody with thoughts on the 2nd question? Its a number grid which I wasn't able to draw :(

Re: Tricky Questions

Posted: Sat Sep 03, 2011 1:10 pm
by no_ball
As a chartered engineer I personally prefer to teach from first principles; then if a question is worded differently but uses the same process, then child is not thrown backwards for six.

Re: Tricky Questions

Posted: Sat Sep 03, 2011 1:16 pm
by Guest55
But your method overcomplicates it - and we are off topic :D

Perhaps that's the difference between mathematicians and engineers :lol: