Comments on: Abstract Algebra

By: ollie

ollie — Fri, 04 Jul 2008 19:46:06 +0000

Ok, for those whose math was a long time ago:

5,000,000! = 5,000,000 x 4,999,999 x 4,999,998 x….x 10 x 9 x 8 x 7….x 2 x 1

For example: 5! is 5 x 4 x 3 x 2 x 1 = 120

How many zeros to the right of 5,000,000 ! written as a whole number means: “how many times does 10 “go into” that number?
10 = 5*2 so this amounts to “how many times does 5 divide this number” since there are more 2 factors than 5 factors.

By: King Aardvark

King Aardvark — Fri, 04 Jul 2008 15:13:24 +0000

Crap. I probably could have solved it in grade 10, but now? Holy crap am I bad at math now (and I’m an engineer). Though, to be honest, factorials don’t come up to often when you’re designing a bridge.

By: BoxerShorts

BoxerShorts — Fri, 04 Jul 2008 13:48:04 +0000

I love math… in principle.

In practice, I lack the mathematical aptitude to be successful at it. I once had aspirations of becoming a physicist, but I gave up on math after first-year calculus and pursued journalism instead.

Which really sucks, because I’m fascinated by math, and I want to be able to understand advanced mathematics. But I can’t. I’m just not smart enough.

By: Steven

Steven — Fri, 04 Jul 2008 12:52:24 +0000

I hate to say it, but I have no idea what you folks are talking about. My last math class was 20 years ago when I bid a, well, less than fond farewell to high school math. I’m going to have to do a lot of catching up in the future to help my kids with their homework.
Is there a “Math for English Majors” handbook out there somewhere?
The most useful bit of “math” I ever learned? How to quickly calculate change due – I never get shortchanged. Sadly, it’s not something they mentioned in school – except for the whole addition thing…

By: Jeff

Jeff — Fri, 04 Jul 2008 03:18:11 +0000

Bartlettman said,
http://www.digicc.com/fido/

I really like that one. Although I haven’t derived the trick yet, I do recognize what the trick is… This will be a fun one to do on people. Definite proof of revelation through the Holy Spirit!!!

By: Back in Peoria, July 2008 « blueollie

Back in Peoria, July 2008 « blueollie — Fri, 04 Jul 2008 02:38:45 +0000

[...] Friendly Atheist is whining about his take home abstract algebra midterm. He gave a sample problem and the readers were able to solve it easily! Problem: how many zeros on [...]

By: efrique

efrique — Fri, 04 Jul 2008 01:15:00 +0000

I’ve done that kind of question before. You just have to count the fives! What’s so hard about that?

By: Hemant Mehta

Hemant Mehta — Fri, 04 Jul 2008 00:28:10 +0000

I independently hit upon the same approach as Duae, DC, and Charles. Really Hemant, don’t tell us that *that* little problem made you cry. I could have done that in like 10th grade.

Fair enough. That was the only problem from the practice test I could actually type into a computer. The rest of it was much more complicated.

So there!

By: Bartlettman

Bartlettman — Fri, 04 Jul 2008 00:08:53 +0000

@Jeff

Maybe they’d enjoy this slightly more complicated puzzle then.

http://www.digicc.com/fido/

If you know the trick you can do it in your head and really shock people.

Then there’s the trick of reeling off the top of your head a huge number that is divisible by 9, you just make sure that pairs of digits sum to 9 (except 0 or 9, which you can use to change the number of digits to an odd number to throw them off)

I love a bit of grandstanding but I get the most enjoyment explaining how these things work to those who will listen (except I don’t want to be a teacher).

By: The Uncredible Hallq

The Uncredible Hallq — Thu, 03 Jul 2008 23:54:09 +0000

I independently hit upon the same approach as Duae, DC, and Charles. Really Hemant, don’t tell us that *that* little problem made you cry. I could have done that in like 10th grade.