Re: [Math4u] Re: Sequence of Operations

I have clarified the rule as follows:

 

1. When addition and subtraction are present together they may also be carried out safely with subtraction first. For consecutive subtractions, use the left to right sequence.

10 – 5 + 8 – 4             =            5 + 4            =            9

3 + 9 – 4 + 7            =            3 + 5 + 7            =            15

5 + 9 – 4 – 7            =            5 + 5 – 7            =            10 – 7            =            3

 

Vinaire

----- Original Message ----
From: Thierry Billette <tbillette@iname.com>
To: Math4u@yahoogroups.com
Sent: Tuesday, December 11, 2007 2:04:37 PM
Subject: [Math4u] Re: Sequence of Operations

I am not sure if I understand Vinaire's rules. For instance how
would the following be evaluated:

9-5-2?

From left to right:
9-5-2 => 4-2 => 2

If you can calculate "minus" first could you have the following:
9-5-2 => 9-3 => 6

To allow "minus" first needs to add that the evaluation must from
left to right if you have several consecutive minus signs. I did not
have time to read Vinaire's thoroughly, I do not know if this case
is included.

Thierry.

--- In Math4u@yahoogroups. com, Rick <rcastrap@.. .> wrote:
>
> Vinaire,
>
> The problem isn't necessarily that your "rule" is incorrect. It is
that
> it is too complicated. What does the beginning algebra student do
if
> there is more than one consecutive subtraction? I think strict left
> association is easier to teach and easier to remember.
>
> -- Rick
>
> --- Vinaire <vinaire@... > wrote:
>
> > When addition and subtraction are present together they may be
> > carried out from left to right.
> > 10 – 5 + 8 – 4 = 5 + 8 – 4
=
> > 13 – 4 = 9
> > 3 + 9 – 4 + 7 = 12 – 4 + 7
=
> > 8 + 7 = 15
> > When addition and subtraction are present together they may also
be
> > carried out safely with subtraction first.
> > 10 – 5 + 8 – 4 = 5 + 4
=
> > 9
> > 3 + 9 – 4 + 7 = 3 + 5 + 7
=
> > 15
> > Mistakes are likely if addition is carried before subtraction.
> > 10 + 8 – 6 + 3 = 18 – 9
=
> > 9 (incorrect)
> > 10 + 8 – 6 + 3 = 10 + 2 + 3
=
> > 15 (correct)
> >
> >
> > Can anybody come up with an exception to the above?
> >
> > Vinaire
> >
> >
> >
> >
>
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> > Never miss a thing. Make Yahoo your home page.
> > http://www.yahoo. com/r/hs
>

---

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