5 + 5 + 5 - 5 + 5 + 5 - 5 + 5 * 0

[Jaffa]

I've tried dividing by zero on calculators.  I was hoping for an implosion or apocalypse of some sort, but all I got was a lousy little 'e' in the corner of the screen.   

[robwebster]

I saw the question and thought, "Welcome to being reminded of how the average person doesn't understand math.

And I mean that in the least hostile way possible. I understand many people don't understand or care about math. As one who's always enjoyed it, it just baffles me how that can be.

I like maths! I was very good at it in school. I took it for A-Levels - so I was a mathematician from start right up to leaving at 18 - and got a pretty good grade.

I also charge bullishly into problems without thinking if they look simple. It's not so much that I don't care about maths, I'm just reckless by nature. I saw "x 0" and thought "right, that's the twist then." I know precisely where I went wrong, why I went wrong, and I'd go as far as to say that in a different context I'd have maybe paid a little more attention to it. As it is, I'm just browsing. So rather than looking for mistakes or analysing the question, I just reverted to my usual nature, which is forgetful, slipshod and a little bit impulsive. I didn't weigh up my options, or even bother adding the fives - just saw the poll and batted at it.

I'll do it again - do it five times again, I'm sure. Doesn't make me a mathsphobe.

EDIT: Ah, I know! It's not my attitude to maths as much as my attitude to instructions. Skim read, blunder in.

[Orbert]

Ha ha, someone else voted for 40.

[MetropolisWatches]

15. Order of operations for the win.

[splent]

dammit... i answered too quickly.  It is 15, I answered 0 because I saw the multiply and forgot you do that first... stupid stupid me

[TioJorge]

dammit... i answered too quickly.  It is 15, I answered 0 because I saw the multiply and forgot you do that first... stupid stupid me

This. Waaay too quickly. I was immediately just like "AW SHIT YOU TRY TO TRICK ME BUT I SMART I KNOW ZERO AND MULTIPLY MEAN ZERO!!!"

Nope... Nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnope.

[theseoafs]

PEMDAS baby.

Now do a problem on Spherical Coordinates, Taylor series or the normalization of quantum wave functions and then we can talk.

Actually, I just ran across a killer logic puzzle (the blue eyes puzzle, if you're familiar with it).  I might post that if I'm feeling particularly sadistic.

[WindMaster]

ITT: stuff we learned in school comes into play in real life.

[TioJorge]

IN THIS THREAD YOU GET THE FUCK OUT




EFF SCHOOL, PARTY HARDY. NUMBERS SUCK. NUMBERS IS COOL. NUMBERS 2 IS A SMARTASS


AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHIM DRUNK n now imma drive to my friends' house so if i keep talking then i'm not dead kbyai

[LieLowTheWantedMan]

TioJorge, ladies and gentlemen!

[kári]

I'm curious what everyone thinks about dividing by zero. That's the real mindfuck.

I'll try to elaborate on this one. Basically you can see why "you can't divide by zero" when you use sequences. A sequence is literally an infinite sequence of numbers. Like 1, 1, 1, 1, .... is a sequence. There are different types of sequences and one of them is a converging sequence. Look at this image:

a sequence converges if and only if there exist a number L, so that for every number e I choose, eventually the "tail" of the sequence will fit into the interval L+e, L-e. Try to think about what this means. For the picture if I pick e = 10000 it's obvious. But it must work for every L so I can pick e = 0.0000000000000000000000000001 etc.
We say that this L is the limit of the sequence.

Anyway, back to "dividing by zero"... But first let's look at the sum 2+3. Obviously it's 5. But we can also see this because of the following.
Take a series that converges to 2, take one that converges to 3 and add them. The sum will converge to 5.
This is obvious. Let's take the sequence 2.1, 2.01, 2.001, 2.0001, ... This sequence obviously converges to 2. In the same way let's take 3.1, 3.01, 3.001, ...
The sum is 5.2, 5.02, 5.002, 5.0002, ... and this sequence will converge to 5.

I could also have taken 1.9, 1.99, 1.999, ... and 2.9, 2.99, 2.999, ... The sum now is 4.8, 4.98, 4.988, 4.998, ... which also converges to 5. No matter what the series is that converges to 2 and to 3, to sum will always converge to 5.
The same is true for any operation like 4+7, 3*27 or 0*5.
Now let's look at for example 2/0. Take any sequence that converges to 2.. for simplicity let's just take the constant sequence 2, 2, 2, 2, ....
Now we can make one that converges to 0 like 1, 0.1, 0.01, 0.001, 0.0001, 0.00001, ...
Now if we divide these we get 2, 20, 200, 2000, 20000, .... as you can see this sequence does not converge to any number, the elements just get bigger and bigger. We say this series diverges to + infinity.

Good. So you could say that 2/0 = + infinity right? Well no because if we take the sequence -1, -0.1, -0.001, -0.0001, ... and use this to divide the constant series that converges to 2 by, we get -2, -200, -2000, -20000, ... Here the elements just get more and more negative and we say this series diverges to -infinity. So 2/0 = - infinity.

And because infinity does not equal minus infinity we can't divide be zero because you get different results depending on how you interpret it.

PS. if you take 0/0 you can get any real number if you construct the series right!

I hope this helps a little.

[Sketchy]

15 with all the primary school BODMAS glory.

... If one of spherical polar involving partial diffs comes up, I'm running. Never did get the hang of those. I could attempt a normalisation though, I guess.