18-06-2012, 18:42   #61
Miss Lockhart
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Quote:
 Originally Posted by equivariant Its really not
Well, that's a matter of opinion really. Why bother posting if you've nothing constructive to add?

Quote:
 Originally Posted by seamus BOMDAS implies that you do multiplication before division and addition before subtraction. This is not the case, it's a result of poor teaching. Multiplication and division have equal priority and must be done in the order that they appear in the equation (starting from the left). In this case therefore you divide 48 by 2 before multiplying the answer by 12. Yes, it's another thing we were all taught incorrectly in school.
Maybe you were taught incorrectly but I wasn't.

It's explained very clearly and correctly in school maths textbooks. Perhaps it was taught poorly to a lot of people but I find it hard to believe it was taught incorrectly by that many teachers.

Also, if you google you will see that this question has been debated on many forums for several years by people from many nationalities. Obviously the confusion is not just down to incorrect teaching here in Ireland.

 18-06-2012, 18:54 #62 sponsoredwalk Registered User     Join Date: Aug 2009 Posts: 2,901 We're equally valid in interpreting 48÷2(9+3) as any one of: 48÷[2(9+3)] = ... [48÷2]•(9+3) = ... 4•[8÷[2(9+3)]] = ... 4•[8÷2]•(9+3) = ... [4•8]÷[2•(9+3)] = ... [[4•8]÷2]•(9+3) = ...
18-06-2012, 20:04   #63
Yakuza
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Location: Dublin
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Quote:
 Originally Posted by sponsoredwalk We're equally valid in interpreting 48÷2(9+3) as any one of: 48÷[2(9+3)] = ... [48÷2]•(9+3) = ... 4•[8÷[2(9+3)]] = ... 4•[8÷2]•(9+3) = ... [4•8]÷[2•(9+3)] = ... [[4•8]÷2]•(9+3) = ...
In chaosland, perhaps. According to convention, it is 48 / 2 x (9 + 3).
If everyone chose to interpret such things according to some whim, chaos would ensue.

18-06-2012, 20:23   #64
bnt
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Quote:
 Originally Posted by Kavrocks Also if I type in exactly what you have in the thread title in to my calculator I get 2. 48/2(9+3) = 2 and 48/2*(9+3) = 288
Can we have make and model, please, so we know what not to buy? We already have three reports in this thread of calculators giving 288: my HP 35 and Casio FX-991ES, and PaulieBoy's TI-89.

I just tried my old Sharp EL-531VH, and that gives 2 if I enter it as written. Never liked that one, anyway, I only bought it in an emergency for an exam ... if anyone wants it, I'll stick it in the post for a Thanks.

19-06-2012, 11:11   #65
seamus
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Quote:
 Originally Posted by Miss Lockhart Maybe you were taught incorrectly but I wasn't. It's explained very clearly and correctly in school maths textbooks. Perhaps it was taught poorly to a lot of people but I find it hard to believe it was taught incorrectly by that many teachers.
It came up here before, and it would appear that a large number of people were taught that BOMDAS is an actual description of precedence. It was only last year that I found out it wasn't; 11 years after I got a B1 in higher-level maths.

It's a little like the rounding issue I discovered before. Straw polls I've done suggest that about 50% of people were taught the incorrect way to round decimals.

This thread also confirms that a lot of people were taught that BOMDAS cites actual order.

Maybe it is right in the textbook, but my experience of maths in school was that textbooks were for problems, not for reference. The teacher explained and demonstrated the concepts, you didn't read them from the book.

What surprises me most is that neither of these incorrect methods were ever discovered either by myself or subsequent teachers; presumably they never resulted in any incorrect answers due to the way tests were written.

I know in State exams in particular, they go to great pains to clearly write out equations to avoid any possible ambiguity about what should be multiplied or divided by something else.

 (2) thanks from: