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 Post subject: money
PostPosted: Sun May 11, 2008 10:39 am 
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Joined: Fri Mar 07, 2008 9:27 am
Posts: 18
Hi
please anyone know this answer?

I owed my brother £10.80 I gave him 2/9 one week and 2/3 next week. Howmuch did I still owe?

I got two answers whitch one is right?
one is £1.20
other one is £2.80


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 Post subject:
PostPosted: Sun May 11, 2008 11:11 am 
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Joined: Sun Jul 22, 2007 8:42 am
Posts: 235
Location: South Warwickshire
I would start by converting 2/3 into 9ths, which I know is 6/9.

So in total (2+6) 8/9 has been paid back.

I would then work out 1/9 of £10.80, which looks easy as I know from my multiplication tables that 12 x 9 = 108, so I can see that 108 divided by 9 is 12, so £10.80 divided by 9 must be £1.20.

So 8/9 must be £1.20 x 8.

I know from multiplication tables again that 12 x 8 = 96, so £1.20 x 8 must be £9.60.

The question asked how much of the debt is outstanding, so £10.80 - £9.60 = £1.20.

Looking back, this doesn't read as simply as I'd hoped. Not sure if I am using the best method!


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PostPosted: Sun May 11, 2008 11:55 am 
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Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11957
Bad dad - you got the same answer at the end of line 4.

This is a poor question because it doesn't make it clear whether both fractions are of the original amount ...


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 Post subject:
PostPosted: Sun May 11, 2008 1:22 pm 
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Joined: Sun Jul 22, 2007 8:42 am
Posts: 235
Location: South Warwickshire
Sorry - see what you mean. And 7/9 x 1/3 x £10.80 = £2.80.

NOTE TO SELF: don't attempt to answer maths questions when you don't know what you are talking about.

Worrying that I am trying to teach my son when I don't really know what I am doing!


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 Post subject:
PostPosted: Sun May 11, 2008 1:31 pm 
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Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11957
The moral is 'read the question' :lol:

The explanation was fine!


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 Post subject:
PostPosted: Sun May 11, 2008 2:04 pm 
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Joined: Tue Jan 01, 2008 1:05 pm
Posts: 515
When I was coaching DS, the problem was not his inability to get the correct answer, but not spotting the quicker ways to do the question. I had problems in getting him to avoid doing unnecessary calculations.

In simple terms, only calculate what you need to know, not what you do not need.

(Assuming the question does relate to the original amount)

then 2/9 and 6/9 is paid back.

therefore 1/9 left to pay.

1/9 of 10.80 is 1.20.


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 Post subject: Re: money
PostPosted: Mon May 12, 2008 8:40 am 
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Joined: Thu Oct 11, 2007 11:51 am
Posts: 14
lala wrote:
Hi
please anyone know this answer?

I owed my brother £10.80 I gave him 2/9 one week and 2/3 next week. Howmuch did I still owe?

I got two answers whitch one is right?
one is £1.20
other one is £2.80


FIRST WE HAVE TO GET 2/9 OF £10.80.WHICH IS £2.40.THEN WE HAVE TO SUBTRACT THAT PAID £2.40 FROM 10.80 WHICH GIVES £8.40.
AND 2/3 OF £8.40 IS £5.60 AND WE HAVE TO SUBTRACT £5.60FROM £8.40.WHICH IS £2.80.AND FINALLY HE OWED TO HIS BROTHER £2.80.


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 Post subject: money
PostPosted: Mon May 12, 2008 8:59 pm 
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Joined: Fri Mar 07, 2008 9:27 am
Posts: 18
Thank for everyone
but still I am confusing which one is correct?


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 Post subject:
PostPosted: Mon May 12, 2008 9:56 pm 
They are both correct depending on how you read the English of the question.
£1.20 is the answer to: I paid him back 2/9 one week and 2/3 (of the original sum) the next week. This would leave him 1/9 to pay which is £1.20.


£2.80 is the answer to : I paid him back 2/9 one week and 2/3(of what I now owe him i.e. £10.80 - £2.40= £8.40) the next week.

It is a highly ambiguous question and I believe either answer would have to be accepted.


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 Post subject: money
PostPosted: Tue May 13, 2008 8:24 am 
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Joined: Fri Mar 07, 2008 9:27 am
Posts: 18
Hi
thanks for your reply

from
lala


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