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 Post subject: Doubling/ halving year 1
PostPosted: Fri Jan 16, 2015 3:25 pm 
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Can anyone tell me what strategies are used for doubling and halving in year 1? DS missed nearly 2 weeks school with flu and they covered this topic in that time and I want to help him. I've been saying to double the units and double the tens numbers, but he got bit confused with 64 ...

Are there any other ways?

Thank you :)


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PostPosted: Fri Jan 16, 2015 3:32 pm 
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It is usually taught by splitting the number ie 64 = 60 + 4 (partitioning)

then 60 + 60 = 120 and 4 + 4 = 8

so 128 altogether.

It is important that they understand that the '6' digit represents 60. (place value)

Halving is the inverse operation so again 64 = 60 + 4

Half of 60 is 30 and half of 4 is 2, so 32 altogether.

I'd check with the teacher the method and language used.


Last edited by Guest55 on Fri Jan 16, 2015 4:16 pm, edited 1 time in total.

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PostPosted: Fri Jan 16, 2015 3:39 pm 
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Thank you so much guest55. I wanted to Ask teacher today but his teacher is off sick now too - probably caught bug off all the children :lol:

I just found he has homework on it so glad I asked here!


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PostPosted: Fri Jan 16, 2015 7:58 pm 
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So, when they are taught to do double 64, and it would be 60+60 = 120 and 4+4=8 how do you get them to add the 60 + 60 bit? Do you say 6+6 but remember it is in the 10s column, so call it 60, or something else??


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PostPosted: Fri Jan 16, 2015 8:20 pm 
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Call it sixty because that's what the 6 digt represents.

https://www.gov.uk/government/publicati ... s-of-study

To me it seems to be a bit early to he doubling and halving such big numbers ...


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PostPosted: Fri Jan 16, 2015 8:53 pm 
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Thanks g55. Ds top table, so maybe that's why the big numbers? He has 5 numbers to double that are in the 100s.


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PostPosted: Fri Jan 16, 2015 9:09 pm 
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I think it's early to be dealing with numbers larger than 100 top table or not ...


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PostPosted: Sat Jan 17, 2015 8:45 am 
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I absolutely agree that there is no need to be doubling such big numbers.

The whole point of the new national curriculum was to get KS1 children to reason well with the skills that they have been taught.

In this case the skill of doubling and halving. Top table should be doing the same as the rest of the class but with more reasoning rather than bigger numbers.

I would start a topic like this with base 10 materials (Diennes).
The children collect their number and then collect that number again. For top table I would get them to use numbers that involve regrouping the ones, such as 26.
To halve they take their number and share it between two circles so that they are developing the skills of division. Again top table can have numbers that involve regrouping the tens into ones, such as 32.

The next step should be to draw the base 10 materials rather than use them.
Finally they should be able to partition the number and regroup without aids. The most able can then apply their knowledge in a word problem.

This is a CPA (concrete-pictorial-abstract) approach and is highly effective in developing children's understanding.


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PostPosted: Wed Jan 21, 2015 1:47 pm 
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I don't know what base 10 materials or diennes or any of that stuff are. It's a good school and ds never had problems picking topics up. I just wanted to help him 'cause he was off sick. He seemed ok with doubling the 3 digit large numbers. Halving large odd numbers tricked him a bit but I got him to divide the even number of tens or hundreds first, then the remaining 10 into 2 groups of 5 or 50. After about 3 goes of that he was comfortable.

Thank you for your help.


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PostPosted: Wed Jan 21, 2015 6:44 pm 
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Location: East Kent
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This is Diennes apparatus, it is really good for seeing how 10 ones make a teb, ten tens make a hundred , ten hundreds a thousand and so on. Makes it visual


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