[Math4u] what is 30%of 152 and 65% of 99

45.6 + 64.35 = 109.95

--- In Math4u@yahoogroups.com, "xixlongvin" <xixlongvin@...> wrote:
>
> ok 26-14=12 and 2*3+4*4=22 so here's one what is 30%of 152 and 65%
> 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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