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 Post subject: dividing with decimals
PostPosted: Thu Mar 06, 2008 6:34 pm 
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Joined: Fri Jan 04, 2008 7:58 pm
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Can anyone please explain this to me

instruction: divide the following and round answer to 2 decimal places

question:- 65.35 / 1.3 answer = 0.129


any help greatly appreciated


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PostPosted: Thu Mar 06, 2008 7:05 pm 
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Something wrong here as the answer you have given has 3dp!


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PostPosted: Thu Mar 06, 2008 8:04 pm 
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sorry, looking at wrong answer :oops: the correct answer is 50.27 but the example in the book is not great and i'm still having trouble working out how to do these sums, so please help if you can.

many, many thanks


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PostPosted: Thu Mar 06, 2008 8:55 pm 
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Usually I would encourage pupils to make sure the number they are dividing by is a whole number so:

65.35 / 1.3 = 653.5 / 13


which will give the same answer - first estimate 650 /10 is roughly 65

What method are you trying to use 'chunking' or 'short division' (Bus stop)

653.5 13 x 50 = 650

653.5 - 650 = 3.5 this is chunking as I'm taking 'chunks off'

3.5 /13 13 x 0.2 = 2.6

3.5 - 2.6 = 0.9

0.9/ 13 13 x 0.06 = 0.78 13 x 0.07 = 0.91 which is nearer

so answer is 50.27 (to 2 dp)

If it's short division you need to look at:

http://www.mad4maths.com/math_help_division/


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PostPosted: Thu Mar 06, 2008 9:06 pm 
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thank you so much, we were only making the 1.3 into whole number and not moving decimal for 65.35 also thanks for the link.


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PostPosted: Thu Mar 06, 2008 9:18 pm 
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It's better to talk about multiplying both numbers by ten -


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PostPosted: Fri Mar 07, 2008 12:29 pm 
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how do you mean?


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PostPosted: Fri Mar 07, 2008 5:26 pm 
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It is not recommended to talk about moving decimal points - if you multiply both numbers by 10 you get whole numbers.


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PostPosted: Fri Mar 07, 2008 5:42 pm 
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I see,

thank you it's much appreciated


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PostPosted: Fri Mar 14, 2008 11:43 am 
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65.35/1.3 - multiply until divisor is a whole number i.e. 13

653.5/13 and then do a short division.

If the sum was 23.6/0.14 you would need to multiply the whole thng by 100 so that you were dividing by 14:

2360/14


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