of 99. --- In Math4u@yahoogroups.com, "Brian E. Jensen"
<brianejensen@...> wrote:
>
> OK, I learn something by making examples:
>
> Example, calculating left to right the correct way:
>
> 2 + 17 - 7 - 5 + 3 = 10
>
> We can do it in any order:
>
> 2 + 3 + 17 - 5 - 7 = 10
>
> We can add the negative terms and subtract them all together:
>
> 2 + 3 + 17 - (5 + 7) = 10
>
> We can perform an addition or subtraction if it comes after an
addition:
>
> (2 + 17) - 7 - 5 + 3 = 10
>
> 2 + (17 - 7) - 5 +3 = 10
>
> We get the wrong answer if we perform an addition or subtraction
that comes after a subtraction:
>
> 2 + 17 - (7 - 5) + 3 = 20 off by 5*2
>
> 2 + 17 - 7 - (5 + 3) = 4 0ff by 3*2
>
> The same is true of multiplication and division because it is the
same as adding and subtracting logs.
>
> Example, calculating left to right the correct way:
>
> 2 * 17 / 7 / 5 * 3 = 2.9143
>
> We can do it in any order:
>
> 2 * 3 * 17 / 5 / 7 = 2.9143
>
> 2 * 3 * 17 / (5 * 7) = 2.9143
>
> We can do a multiplication or division first if it doesn't follow
a division:
>
> (2 * 17 ) / 7 / 5 * 3 = 2.9143
>
> 2 * (17 / 7 ) / 5 * 3 = 2.9143
>
> We get the wrong answer if we do a multiplication or division
first that follows a division:
>
> 2 * 17 / 7 / (5 * 3) = 0.3238 which is off by a factor of 3^2
>
> 2 * 17 / (7 / 5) * 3 = 72.857 which is off by a factor of 5^2
>
> So there's the requested examples. I was thinking of letting it
drop, but I learned something making these examples. As it becomes
clearer in my mind, it seems like nothing to argue about.
>
> Sorry,
>
> Brian
>
>
> ----- Original Message -----
> From: Asif Lodhi
> To: Math4u@yahoogroups.com
> Sent: Tuesday, November 27, 2007 5:24 PM
> Subject: Re: [Math4u] Re: 26 - 14 : 2 x 3 + 4² = ?
>
>
> Hi Brian,
>
> On 11/28/07, Brian E. Jensen <brianejensen@...> wrote:
> > answer. As Vinaire's method avoids, if you have a plus term
that follows a
> > negative term, you cannot add the plus term to the negative
term or you will
> > be subtracting the plus term from the final result instead of
adding it to
> > the final result. Similarly, if you have two minus terms next
to each other,
> > you cannot perform the second subtraction first or you will
wind up adding
> > it to the final result instead of subtracting it from the
final result.
>
> It would help the list users if you could elaborate the above
text
> with some examples.
>
> > consider this a heresy and a threat to western civilization.
>
> I don't think so. Research into anything is always good. I don't
think
> any research is a heresy or a threat to any civilization. We
just get
> to learn more that way. After all, we are all here to find out
more
> about maths! :) It doesn't matter who's coming from where.
>
> --
> Best regards,
>
> Asif
>
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