# 48÷2(9+3) = ???

Discussion in 'Bad Dog Cafe' started by Agave_Blue, Apr 9, 2011.

## 48÷2(9+3) = ???

190 vote(s)
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1. ### Agave_BlueFriend of Leo's

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Uhhmmm, not really "OK".

Brackets first = OK

But now I can choose to divide before multiplying; which changes the answer.

IOW:

48/2(12) = 24(12) = 288

2. ### Agave_BlueFriend of Leo's

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http://www.mathgoodies.com/lessons/vol7/order_operations.html

3. ### chezdeluxePoster Extraordinaire

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If you express the problem algebaically as 48 divided by 2y where y= (9+3) the answer is obviously 2.

If you express it as 48 divided by 2 Multiplied by y where y= (9+3) the answer is 288. There is no multiplication sign between the 2 and the bracket so the 2(9+3) operation must be completed totally as a bracket operation first.

I think????

4. ### ' burn 08Tele-Afflicted

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It's 2. In fact I'm not sure how anybody sees pemdas as making it 288. Pemdas would say that (48/2)(9+3)=288. But 48/2(9+3)=2. The 2 distributes to the
9 and 3. If your calculator days 288 try a graphing calculator. You can program it in as am equation. A regular calculator does not read it as am equation and there for does not follow the rules of pemdas. Normal calculators perform the mathematical calculations in the order of appearance.

5. ### TGDoctor of Teleocity

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In my mind you'd put an X between the 2 and the bracket if you were meant to divide 48 by 2 and then multiply by (9+3) as a separate stage. Otherwise I see 2(9+3) as the thing 48 is to be divided by.
Not having a multiplication sign signifies that the 2 is multiplied by the (9+3) alone, IMO. And first.

I'm sticking with 2.

6. ### Jimclarke100Tele-Afflicted

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Yeah you're right - It comes back to me now a little (College was 25 years ago and several glasses of wine don't help!). As my alcohol fiddled brain now pulls up, multiply and divide have the same priority so the sum as written doesn't have the information to correctly solve it... so need more brackets to be sure.

Still thinks it's 2 though...

7. ### ' burn 08Tele-Afflicted

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Also, that's just a bad way to write an equation.

8. ### jbmandoPoster ExtraordinaireGold Supporter

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I agree with this. For it to be 288 it has to look like this: (48 ÷ 2)(9+3)

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Yup!

10. ### Agave_BlueFriend of Leo's

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2 of the 4 "graphing" calculators in the 1st post say "288" and two say, "2".

My Ti-83+ "graphing calculator" says 288.

Excel says, "288"; so does Java and, iirc, so do PERL, C and C++.

11. ### TGDoctor of Teleocity

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Which is what I was trying to say.
Otherwise you do the brackets first, correctly...and then the 2 and the 12 are sitting there side by side, ie, '48 divided by 2 12'. You can't have that as a step.

It's 2.

12. ### BolideFriend of Leo's

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You forgot to square the unit:
3 guitars X 3 guitars = (3x3) X (guitars x guitars) = 9 square guitars.

13. ### jbmandoPoster ExtraordinaireGold Supporter

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Alt + 0247 = ÷ on a windows machine. Can't help you for a Mac.

14. ### Guitar_NinjaFriend of Leo'sAd Free Member

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I own the Casio calculator on the upper right and use it far too much every day. You need to put the 2(9+3) in brackets if you want to divide 48 by 24:

48/(2(9+3))

Otherwise it will divide 48 by 2, then multiply the answer by (9+3). Effectively,

(48/2)*(9+3)

Believe me, it's screwed me up on more than one exam.

15. ### Agave_BlueFriend of Leo's

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Well, we don't get to do that.

The problem is written as 48÷2(9+3), so adding misc brackets changes the problem.

16. ### flathdPoster Extraordinaire

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I went with 2 right off the bat. Even if its wrong majority wins, right?

17. ### ' burn 08Tele-Afflicted

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Dang. I thought for sure the calculator thing would settle it. I don't even know where my ti82 is. Programs like C++ and matlab have a specific order of operations. I don't remember what that is though. I haven't done any programming in a few years.

18. ### The ZesusTDPRI Member

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2

It's a good thing engineering isn't done by people who base their math on popular opinion.

Calculators, like all tools, require the user to be smarter than the tool itself.

19. ### Agave_BlueFriend of Leo's

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They don't know either: http://www.physicsforums.com/showthread.php?t=488334

20. ### telemnemonicsTelefiedAd Free Member

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This is like more than three knobs on a pedal

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