Re: [Math4u] Sequence of Operations

Rick,

 

As I said earlier, your point is well taken. However, it is good to know the rule I have stated (modified for consecutive minus signs), as it simplifies mental calculation of many situations, such as,

 

365 + 597 - 592 + 604 - 601  =  365 + 5 + 3  =  373

 

We were taught this procedure in India, and it didn't appear very complex to me when I was a kid.

 

Vinaire

----- Original Message ----
From: Rick <rcastrap@yahoo.com>
To: Math4u@yahoogroups.com
Sent: Tuesday, December 11, 2007 12:09:31 PM
Subject: Re: [Math4u] Sequence of Operations

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@yahoo. com> 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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