48÷2(9+3) = ??

Looks like there are multi-page threads of this question sweeping the interwebs. I am not sure we can outsmart the various math geeks that are arguing about it. The expert opinion leans toward the answer of 288 but only a moron would write the equation that way. That is what I thought in the first place.

3 guys check into a hotel room and are charged $30. Later the clerk realizes they should've only been charged $25.......

haha TJ and I want that shirt

I guess I was so defending on 288 because it is basic math and to use PEMDAS. I always thought M and D along with A and S cancelled each other out but technically the only thing that gets cancelled out are negative numbers. Also when you change to a horizontal division sign it changes the whole problem around with the answer definetly being 2, all in all you want to simplify it to simplest terms....ALWAYS, so with it being written like THIS confuses people and confuses them when they are using PEMDAS.........I'm seein it clearly!!!

I still say Miata

fast_eddie_72 wrote: I said all that on page one. So why don't we get the same answer. And why do you do the multiplication before the division when the division comes first.

Because I'm doing the bracketed term (2 x (9+3)) first. This is more shortly written as 2(9+3). Like I said a bazillion times, you have to read the equation and determine its structure correctly before you go blindly in pimp-slapping everything with BEDMAS until it cries.

The structure of this equation is "one simple term÷one expanded term". As there are really only two terms and one operation, the L-R convention doesn't enter into it.

fast_eddie_72 wrote: Jay, I'm sure you're not making this up. I tried to find this rule somewhere. I don't know enough about it to make the google machine work. Can you just post a link to something that explains how this works? I think that would end this quickly.

I just tried to find something but pretty much any search of related terminology on Google brings back only a flood of links to "48÷2(9+3)=?" threads. I think we've managed to bork up math research for the next few generations... Nice going, internet nerds.

The whole thing was clarified to me in a really good linear algebra textbook I had in my 1st(?) year of university. I can't remember what the book was or who it was by though. Sorry if that's useless.

I am SO getting bumper stickers of this equation.

Jay wrote: Because I'm doing the bracketed term (2 x (9+3)) first. This is more shortly written as 2(9+3).

Jay, I'm not arguing with you. It sounds like you know what you're doing.

You're making an assertion. You say 2(9+3) is the same as (2x(9+3)). You may very well be right. As I've said, math isn't my thing. I'm just asking you to post a link to something that clearly shows that your assertion is accurate. I'm inclined to think you're right. It's unlikely you just made it up. But I'm not familiar with it and it looks like a lot of other people here aren't either.

Just post up a link that explains that and we'll all be on the same page. I took a little time last night to try to find it and could not. I just came up with more order of opperations stuff. We all seem to agree on that. But none of it addressed the implied "x". You seem to have experience with a rule that does address that. I'd be interested in learning more about that.

hahahaha Ben, I was literally thinking that reading all this

BTW, a coworker sent this to his dad, who's a Ph.D. math prof. I'll post up his reply if/when I get it.

Looks like we were typing at the same time.

Well, it is what it is. You could be right. Dunno.

The way it's written, the answer is 288. 48÷2(9+3) = 48/1 x1/2 x (9 + 3)/1= 48/2 x (9 +3) = 48/2 x 9 + 48/2 x 3 = 24 x 9 +24 x 3 = 288. Instead of dividing, think of mulitpling by the inverse; you'll see that the "(9+3)" stays in the numerator and therefore you get 288.

nice ^

that's my 48/2(9+3) cents

fast_eddie_72 wrote: Jay, I'm not arguing with you. It sounds like you know what you're doing. You're making an assertion. You say 2(9+3) is the same as (2x(9+3)). You may very well be right. As I've said, math isn't my thing. I'm just asking you to post a link to something that clearly shows that your assertion is accurate. I'm inclined to think you're right. It's unlikely you just made it up. But I'm not familiar with it and it looks like a lot of other people here aren't either. Just post up a link that explains that and we'll all be on the same page. I took a little time last night to try to find it and could not. I just came up with more order of opperations stuff. We all seem to agree on that. But none of it addressed the implied "x". You seem to have experience with a rule that does address that. I'd be interested in learning more about that.

Sorry, that wasn't meant to sound all defensive. I just thought the line about pimp-slapping was too amusing not to work in there.

The level of animosity will drop if you add this to end of everyone else's post.

My QA team rejected the mathematical expression as written, due to usability concerns.

RossD wrote: The way it's written, the answer is 288. 48÷2(9+3) = 48/1 x1/2 x (9 + 3)/1= 48/2 x (9 +3) = 48/2 x 9 + 48/2 x 3 = 24 x 9 +24 x 3 = 288. Instead of dividing, think of mulitpling by the inverse; you'll see that the "(9+3)" stays in the numerator and therefore you get 288.

You don't multiply by the inverse of 2, you multiply by the inverse of 2(9+3). If it were written as "48 ÷ 2 × (9+3)" then you could re-write it as "48 × ½ × (9+3)" but that's not how it's written so you can't do that. Otherwise you're saying 2(9+3) = ½(9+3) which is obviously not true.

eight pages of arguing, and the only solid conclusions are that the original question was written to be ambiguous.

48/2(9+3) can either be interpreted as 48÷2×(9+3) or as

48

2×(9+3)

which leads to the question of whether 2(9+3) infers 2×(9+3) or (2×(9+3)).

Bottom line? Garbage in = Garbage out, and without an ultimate authority to arbitrate whose interpretation and inference is correct you just have a shouting match.

In reply to nderwater:

Yes.

Thanks GOD!

I FOUND the ANSWER! We can finally put this to bed.

Turns out this thing is all over the internt. It is a fairly rescent deal though, so it took a little bit to find this. Turns out that two highly regarded mathmatics authorities took the time to explain this because they found it an interesting opportunity to explain some areas where math can be confusing. There's some language here that's over my head, but I got the jist of it. Well, take a look for yourselves. Obviously, plenty safe for work. Just a couple of math wonks talking about this math problem.

http://www.youtube.com/watch?v=wv19iAncrrQ&feature=player_embedded

Jay wrote: Sorry, that wasn't meant to sound all defensive. I just thought the line about pimp-slapping was too amusing not to work in there.

No problem. It's more complicated than I realized. See the video above. I think you'll like what they have to say on this.

nderwater wrote: Bottom line? Garbage in = Garbage out, and without an ultimate authority to arbitrate whose interpretation and inference is correct you just have a shouting match.

Hey, we're having a rational, intelligent debate. I'm not shouting!

...
Well, maybe a little.

fast_eddie_72 wrote: Thanks GOD! I FOUND the ANSWER! We can finally put this to bed. Turns out this thing is all over the internt. It is a fairly rescent deal though, so it took a little bit to find this. Turns out that two highly regarded mathmatics authorities took the time to explain this because they found it an interesting opportunity to explain some areas where math can be confusing. There's some language here that's over my head, but I got the jist of it. Well, take a look for yourselves. Obviously, plenty safe for work. Just a couple of math wonks talking about this math problem. http://www.youtube.com/watch?v=wv19iAncrrQ&feature=player_embedded

Wish i could see this. Dammit i just want to know that i'm right!

Jay, throw something through your monitor if they say it's 288, i might be able to hear it from here.

YouTube is blocked at work - what was their verdict?

As I understand it, the problem is intentionally vague. Either answer can be "right" if you follow different, conflicting rules. That's the point of the problem. It shows that it is possible to create an equation with two "right" answers. It is designed to show that issue.

I can't explain it that well. The guys in the video I posted above say it better than that. Watch it when you get home.

Get the T Shirt here: http://www.zazzle.com/48_2_9_3_tshirt-235882834792365529