11 Plus Exams Forum

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

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 '-'

10f+3(4-2f)

start with multiplying out teh brackets

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

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!
Appreciate your help

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

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

Thank you so much
I still don' t get it but she does! Hey Ho ! Think I need Rehab!
Thank you so much

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

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!

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