# Re: Is anyone contributing? (fwd)

Anne Huffer (huffera@mail.firn.edu)
Tue, 10 Jun 1997 06:47:29 -0400

Judy Ann Brown wrote:
>
> Hi
>
> I though this message suggests an interesting topic for conversation. Please cc
> the original news group <TTalk@MathCentral.uregina.ca> in your replies
>
> Judy
>
> ------------ Forwarded Message begins here ------------
> From: "Teacher Talk" <TTalk@MathCentral.uregina.ca>
> Date: Mon, 09 Jun 1997 19:51:35 -0700
> To: TTalk@MathCentral.uregina.ca
> Subject: Re: Is anyone contributing?
>
> Ruth, it looks like we are the only two people at home. I subscribed three
> weeks ago and yours was the very first e-mail I received from TeacheTalk.
>
> Well, what if we start talkiing about math? Let me propose the following
> question:
>
> If we insist that 6x3 and 6(3) both mean multiplication. And the order of
> operations says to compute multiplication and division in order from left
> to right, why do we get different answers on a graphing calculator when we
> calculate 6/3x(4 + 2) and 6/3(4 + 2)?

Check out several calculators:

On the TI '82 and '85 and Cassio color there are two answers -> 12 when
the "*" is entered for multiplication and .33333... when only the "()"
are used. On the TI '92 and on the HP38G, the only answer is 12 for both
forms. On the HP48G the answer is 12 when the multiplication is entered
and an error message "invalid syntax" is given when it is left out -
forcing the entry of the multiplication sign. The calculator, after all,
uses a programmed routine to evaluate expressions. On those that give
two answers the lack of a multiplication sign forces 3(4+2) to be
considered together as the denominator of the fraction whose numerator
is 6. Obviously the '92 and 38G use the order of operations we are all
familiar with. This is a very good reason for telling students "when in
doubt - parenthesize".

Anne Huffer
huffera@mail.firn.edu