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 Post subject: Algebra questionPosted: Sat Mar 18, 2017 6:04 pm

Joined: Wed Feb 01, 2017 6:51 pm
Posts: 5
My son is revising for his test on Monday and has found a question quite hard to do. He has looked up the answer to be -4 but hes not sure how it gets to that. Could anyone explain:
Solve for D
(D+7/3)+4=- 5d/4
OR

D+7 -5d
------ +4= - ---- (to make it a bit clearer)
3 4

Thanksss

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 Post subject: Re: Algebra questionPosted: Sat Mar 18, 2017 6:09 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14648
I'm still not clear what the question is but if there are fractions then a good first step is to multiply through by the LCM of the denominators.

So multiplying by 12 gives

4(d + 7) + 48 = - 15d

Now get him to finish it.

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 Post subject: Re: Algebra questionPosted: Sat Mar 18, 2017 7:15 pm

Joined: Sat Oct 22, 2016 5:37 pm
Posts: 148
then open up the brackets, BODMAS rule

4d+28+48 = -15d
4d+76=-15d
19d=-76
d=-76/19
d=-4

quod erat demonstrandum

love algebra

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 Post subject: Re: Algebra questionPosted: Sat Mar 18, 2017 8:49 pm

Joined: Sun Sep 18, 2016 7:28 pm
Posts: 41
Solved!

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 Post subject: Re: Algebra questionPosted: Sat Mar 18, 2017 11:00 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14648
timothylewin wrote:
then open up the brackets, BODMAS rule

4d+28+48 = -15d
4d+76=-15d
19d=-76
d=-76/19
d=-4

We don't 'open up' brackets and the normal rule is BIDMAS these days. I'm sure the OP didn't need the detail and it is good practice not to give full solutions - that is not 'helping'.

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 Post subject: Re: Algebra questionPosted: Sun Mar 19, 2017 9:52 am

Joined: Sat Oct 22, 2016 5:37 pm
Posts: 148
I open up the brackets, lets agree to disagree.

Also if you read the question from the OP carefully, the OP states 'Solve for D', rather than leave it hangin'. QED (again).

It is very good practice to give the detail as then the OP can make the final judgment as to what to show and what not to show little jimmy. Rather have all the information than half a story. Not all OP's excel in these algebraic matters. You have my feedback.

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 Post subject: Re: Algebra questionPosted: Sun Mar 19, 2017 10:27 am

Joined: Sat Oct 01, 2016 5:02 pm
Posts: 695
My Y6 son is still being taught BODMAS. He says BIDMAS is just a different word for 'order' but he can't remember what the I stands for instead. Is that right?

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 Post subject: Re: Algebra questionPosted: Sun Mar 19, 2017 10:33 am

Joined: Thu Mar 12, 2015 4:11 pm
Posts: 229
It's the same thing. The letter I stands for indices. For examples in 2 to the power of 3, the index is 3.

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 Post subject: Re: Algebra questionPosted: Sun Mar 19, 2017 11:10 am

Joined: Sat Oct 22, 2016 5:37 pm
Posts: 148
indeed, BIDMAS and BODMAS, same thing. Maybe its a regional thing like accents

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 Post subject: Re: Algebra questionPosted: Sun Mar 19, 2017 12:28 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14648
timothylewin wrote:
indeed, BIDMAS and BODMAS, same thing. Maybe its a regional thing like accents

QED should only be used when dealing with formal proofs which this question was not - please use the correct terminology for 'expanding' brackets or you are leading students astray.

BIDMAS is the new form of BODMAS as 'order' is not used. The' I' represents 'indices'.

The poster wanted help - which is what I gave - it is not good practice to complete a solution for someone. An effective teacher just gives a hint ...

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