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 Post subject: Finding a factorPosted: Mon Apr 06, 2015 10:45 pm

Joined: Thu Apr 04, 2013 8:19 am
Posts: 107
Can people help please? I don't know what to start. The question is - The factors of a number add up to 13. What is the number? How do we do this please?

Thank you

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 Post subject: Re: Finding a factorPosted: Tue Apr 07, 2015 6:24 am

Joined: Mon Jun 18, 2007 2:32 pm
Posts: 7065
Location: East Kent
Factors are 2 numbers which you multiply together to make a given number..

E.g factors of 12
are 1, 2, 3, 4, 6 and 12. ( 1x 12; 2x6; 3x4)

so for this you could find 2 numbers which add up to 13 and multiply them together.

There is more than one answer, was it a multiple choice question?

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 Post subject: Re: Finding a factorPosted: Tue Apr 07, 2015 7:12 am

Joined: Mon Jun 23, 2014 9:58 am
Posts: 10
Location: Croydon
I think they want all the factors of a particular number, so start with 2:

the factors of 2 are 2 and 1 (2 is divisible by 2 and 1 only), so adding them together will get 3 (2+1=3)

then 3 - the factors are 3 and 1 only, so 3+1=4

for 4 - the factors are 4, 1 and also 2, because 4 is divisible by 2 also, so the sum of the factors will be 4+1+2=7

for 5 - the factors are 5 and 1 only, so 5+1=6
for 6 - the factors are 6, 1 and also 2 and 3, so 6+1+2+3=12
for 7 - the factors are 7 and 1 only, so 7+1=8
for 8 - the factors are 8, 1 and also 2 and 4, so 8+1+2+4=15
for 9 - the factors are 9, 1 and also 3, so 9+1+3=13 - BINGO!

hope that helps

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 Post subject: Re: Finding a factorPosted: Tue Apr 07, 2015 8:45 am

Joined: Mon Jun 18, 2007 2:32 pm
Posts: 7065
Location: East Kent
Doh! How many times do I tell my pupils......

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 Post subject: Re: Finding a factorPosted: Tue Apr 07, 2015 9:04 am

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 13043
The number must be less than 13 so I would have worked down from there ...
13 - can't be
12 - has lots of factors so not that
11 - no - it's prime so 11 + 1 = 12
10 - again too many factors
9 - yes, 1 + 3 + 9 = 13 (what do you notice about the sum of factors of a square number?)

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 Post subject: Re: Finding a factorPosted: Wed Apr 15, 2015 9:39 am

Joined: Thu Apr 04, 2013 8:19 am
Posts: 107
Sorry everyone for late reply - Internet went for long spaces of time. DH thought it only worked when we asleep

I think we need to play with factors to get this. Your replies so helpful. Thank you

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 Post subject: Re: Finding a factorPosted: Wed Apr 15, 2015 1:25 pm

Joined: Mon Jun 18, 2007 2:32 pm
Posts: 7065
Location: East Kent
Lots and lots of board and dice games and interactive stuff online if you goggle factor games. I play them with my pupils, the competitive spirit takes over and they can spot them really quickly!

Eta: I meant google!

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 Post subject: Re: Finding a factorPosted: Thu Apr 16, 2015 10:22 am

Joined: Thu Apr 04, 2013 8:19 am
Posts: 107
Thank you yoyo123. I look for them.

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 Post subject: Re: Finding a factorPosted: Thu May 07, 2015 11:48 pm

Joined: Wed Mar 11, 2015 7:48 pm
Posts: 23
Please see Khan Academy videos on youtube. My DS was always confused till he saw those and now he is very confident/quick and accurate. You can see them for other topics as well.

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 Post subject: Re: Finding a factorPosted: Fri May 08, 2015 8:25 am

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 13043
Please don't use Khan Academy without being aware of the issues with it from a maths teacher's point of view.

I won't go on about it, as I've mentioned this before, but its American and uses non-UK methods and vocabulary. It's more likely to confuse than help.

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