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 Post subject: Homework help pleasePosted: Tue Oct 16, 2007 7:24 pm
Guest55
Hope you are online and can help with this
yr 7 dd homework has me stumped!
10f+3(4-2f)
where the ecky peck do I explain this to her
she says she has the answer but would like clarification
Her answer is 16f +12

Any help would be much appreciated

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 Post subject: Posted: Tue Oct 16, 2007 7:30 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11955
10f+3(4-2f)

the number in front of the bracket is shorthand for 'mutiply everything inside this bracket by me' so

10f+3(4-2f) = 10f + 12 - 6f 3 x 4 = 12 and 3 x -2f = -6f

collecting like terms gives the answer as 4f + 12

I think your cherub forgot the '-'

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 Post subject: Posted: Tue Oct 16, 2007 7:32 pm

Joined: Mon Jun 18, 2007 2:32 pm
Posts: 6966
Location: East Kent
10f+3(4-2f)

multiply everything in teh bracket by 3 x4 =12
3x -2f= -6f

so you have 10f +12 -6f

collect like terms together

10f - 6f +12

10f -6f = 4f

answer if 4f +12

Looks as though she didn't notice it was MINUS 2f

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 Post subject: Posted: Tue Oct 16, 2007 7:46 pm
Guest55
thank you so much for your reply, I appreciate it v much.
I hope you aren't offended, only mildy amused that dd thinks you are wrong.

I have tried to explain to her that you are a very nice helpful grammar school maths teacher but LOL she thinks you are wrong
Her teacher told her how to do the questions and that is what she has done. She is very confused as she is being told two different methods with two completely different answers.
She typed the last bit by the way?
Oh who would be a parent?
what is ' ' by the way
I'm so lost I make Marc Thatcher look good!

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 Post subject: Posted: Tue Oct 16, 2007 8:06 pm
oh deary deary me
dd tears and tantrums, would like to know why the bit in the bracket makes the 2f a minus number seems to assume it is simply 4-2f I'm struggling?
Appreciate your help so much

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 Post subject: Posted: Tue Oct 16, 2007 8:21 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11955
No, I'm not offended - been teaching far too long for that

the ' ' had a minus in between - her answer seemed to imply she had said 3 x 2f = 6f forgetting that the '2f' had a minus sign in front.

Try another example [if you dare!!]

10x + 4(3 - 2x) = 10x + 12 - 8x 4 x 3 = 12 and 4 x -2x = -8x

so the answer is 2x + 12

GOOD LUCK!! SOme teaxhers use thegrid method to help explain brackets ...

http://www.bbc.co.uk/schools/ks3bitesiz ... ts_1.shtml

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 Post subject: Posted: Tue Oct 16, 2007 8:35 pm
Thank you so much
I still don' t get it but she does! Hey Ho ! Think I need Rehab!
Thank you so much

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 Post subject: Posted: Tue Oct 16, 2007 8:38 pm
Further to the above (very correct) answers...
When dealing with brackets in algebra, always remember that everything inside the bracket must be multiplied by whatever is immediately outside of the bracket.
In this case the '3' is immediately outside the bracket. Therefore,
3 x 4 = 12
3 x -2f = -6f.
Looking back at the question, 10f + 3(4 - 2f)
we have,
10f + 12 - 6f.
Collecting like terms we have, 4f +12.
Hope this helps. Good luck
abcdef

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 Post subject: Re: Homework help pleasePosted: Tue Oct 16, 2007 8:59 pm

Joined: Fri Jul 06, 2007 8:31 pm
Posts: 1192
Stumped wrote:
10f+3(4-2f)

Her answer is 16f +12

Any help would be much appreciated

There is of course an easy way to check!

Choose a number... say 1 and substitute...

10f+3(4-2f)

10x1 + 3 (4-2x1)
10 + 3 (4-2)
10 + 3 (2)
10 + 6
16

now try...

16f +12

16 x 1 + 12
28

16 is not 28

Therefore 16f+ 12 is not the answer!

As you already know... the answer is...

10f+3(4-2f)
10f + 3x4 -3x2f
4f + 12

Let's try it again with 1

4x1 + 12
16

Hey Presto!

_________________
Animis opibusque parati

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 Post subject: Posted: Thu Oct 18, 2007 10:11 am
Stumped don't worry about it as I am completely 'stumped'. I can never get my head around these but sad as it may seem I would like to(woudl help when daughter goes to secondary s in 09) . Can someone set out a very simple one to start me off just so as I can get some sort of understanding.

If I could understand atleast some of this maths my son may stop sighing at me and giving me that look with the frown and tilted head when I ask if I can be any help with his math homework(year .

Perhaps we need another topic called

'Further education for us parents'

Mel

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