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PostPosted: Tue Sep 27, 2011 11:27 am 
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It's from one of the bond books.

How many times can I take 39 from 624.

Normally, I would suggest these be done as straightforward division-but this is quite hard! I did it quickly by chunking
39 x 10=390 (624-390= 234)
39 x 5= 195 (234-195=39)
39 x 1= 39
so 16 x 39 = 390

Would you tend towards getting them to do more traditional division in these questions?


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PostPosted: Tue Sep 27, 2011 12:18 pm 
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I would go with which ever method they feel happiest with, if that is chunking then fine as long as the answer is right!


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PostPosted: Tue Sep 27, 2011 3:34 pm 
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I'd get them to estimate first .... :D :D


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PostPosted: Wed Sep 28, 2011 11:16 am 
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If you knew it didn't have a remainder then it's really quick as you see the answer has to end with a 6, and 26 is too big, and 16 is too small, but otherwise whatever is the fastest method for that child? If they were good at pretty accurate chunking, and you had loads of preparation time, I guess I personally would move towards more formal methods if that was feasible for that particular child and would lead to greater speed and accuracy.


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PostPosted: Wed Sep 28, 2011 11:17 am 
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oops meantto say 6 is too small


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PostPosted: Wed Sep 28, 2011 12:45 pm 
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Sorry to be really thick Mystery, but why does it have to end with a 6?

My DD had a Q like this, and started chunking, but it took ages and she didn't get the right answer in the end.

Is there a simple explanation for really struggling mothers?


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PostPosted: Thu Sep 29, 2011 12:11 pm 
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.


Last edited by Belinda on Thu Nov 01, 2012 1:18 pm, edited 1 time in total.

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PostPosted: Thu Sep 29, 2011 5:18 pm 
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I'll be bold and show my ignorance here. Mystery, how do you know the answer must end in a six?

I'd just go down the straight long multiplication route. They haven't touched on it at school yet. If they don't soon I'll have to teach them and they don't understand my old maths approach.

.


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PostPosted: Thu Sep 29, 2011 5:32 pm 
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Location: East Kent
menagerie wrote:
I'll be bold and show my ignorance here. Mystery, how do you know the answer must end in a six?

I'd just go down the straight long multiplication route. They haven't touched on it at school yet. If they don't soon I'll have to teach them and they don't understand my old maths approach.

.


chunking leads on to long multiplication really well and helps them understand what is happening with long division.

which ever method you use, the estimation is a really good first step


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PostPosted: Thu Sep 29, 2011 5:37 pm 
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Have just asked DS1 to do this sum..a nice little post dinner teaser for him... and he came to 16 straight away and said he multiplied 39 by 10 to get 390 and then just added on each 39 up to 624.Not sure if that's the easiest way ?


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