> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
> Of RussellMc
> Sent: 13 March 2012 14:53
> To: Microcontroller discussion list - Public.
> Subject: Re: [OT] Maths fun
>=20
> > Nonsense,
>=20
> ?
>=20
> > the answer should be according to the rules of the system at
> > hand! If a system does not adhere to its own rules it is wrong, but whe=
n
> > it has strange rules it is just strange.
>=20
> I am saying that the answer to
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>     6/2 * (1+2)
>=20
> as written, and based on the "proper" [tm] rules of mathematics =3D 9.
> I am saying that "1" is an incorrect answer.
> Do you disagree in either case?
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> If you do disagree, do you hold that " * " is not commutative?
> Or ... ?
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> Is:
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> 6/2 * (1+2)  =3D =3D  (1+2) * 6/2 ?
>=20
>=20

Russell,

Multiplication is commutative, but obviously division is not.  If the opera=
tions in the equation as originally written are performed in the order taug=
ht to children in the UK i.e. "BODMAS" then the division would be performed=
 before the multiplication and the result will be 9.  This appears to form =
the basis of your argument.

However, this thread has already shown that in the US at least, children ar=
e taught a different mnemonic (PEDMAS) which puts multiplication ahead of d=
ivision in the ordering, and which yields a result of 1.

This suggests that you can not guarantee that the order of evaluation that =
someone will apply will be the same as your own, so parentheses should be u=
sed if there is any ambiguity in the expression.

Mike


I sent that a little prematurely - the mnemonic that puts multiplication fi=
rst is "PEMDAS".

Mike

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
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=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

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