Math Quiz

[chess9]

MisterT: Oh, there must be at least one extra zero, right? 201?

 

[M00T]

2 * 13 = 26
13's the magic number

 

[Duckers]

M00T, you are a nef!

 

[Mister T]

200 and 201 is still wrong.

BA

Go ahead and give the answer. Explain your reasoning too.

 

[0beron]

100

 

[Duckers]

MrT, why don't you tell us the answer ?

If you are able to ask a question then I guess you should be able not only to give the answer but also to explain it...

 

[BA]

249

Edit: reworded for clarity

The number of zeroes following a factorial is equal to the number of 5 factors(a factorial has more 2 factors than five, so for every 5, there's a 2 to multiply it by, giving you a factor of 10, and therefore a zero on the end). So 10! has 2 trailing zeroes, from 5 and 10.

So simply dividing by 5 appears to work, but what happens when you get to 25? 25 is 5x5, so it will cause 2 trailing zeroes, as will every multiple of 25.
Then for every multiple of 125, you get 3 zeroes; and 625, 4.

so, 1001 is followed by (1001/5)+(1001/25)+(1001/125)+(1001/625)=249.

 

[chess9]

Ooh, very pretty. I missed that in Middle School!

 

[chipbgt]

Thanks guys, after reading this post My brain has hopped out of my head via my ear and is cowering in the corner in terror.

 

[Duckers]

BA, are you sure you learned that in middle school or was it in the elementary school ?

 

[Capn]

pffff I'd rather waste my time on applicable math techniques,

 

[BA]

Well, it's not one of those things you learn unless you're in the nerd contest circuit. There a limited number of different types of problems they'd give you, you just had to learn all the patterns. And it was actually almost useful for me. In Mathcounts, the top 4 individual places go to nationals, get out of school and get a bunch of free crap; I got 5th in 7th and 8th grade. Had to wait for AcaDec to get to a national competition in anything(At which, interestingly enough, I got 4th in math. Top 3 places got medals...)

 

[Duckers]

I have a question for you guys, I do not know how to figure out the answer but I know what it is.

A woman drove to work at an average speed of 40 miles per hour and returned along the same route at 30 miles per hour. If her total traveling time was 1 hour, what was the total number of miles in the round trip ?

BTW, the answer is not 35.

 

[Capn]

17.14285714 miles,

 

[Duckers]

Capn, you are close.

 

[Duckers]

btw, explain your reasoning so we all can learn something new...

 

[Capn]

ahh you said round trip, in that case it'd just be 34.28571429 miles I believe

My solution

distance/rate = time

We know the rates, and the total elapsed time.
We'll use X for the distance one way, then we can say

(X/30) + (X/40) = 1

Then, all you got to do is multiply both sides by 1200 and solve for X

 

[chess9]

BA: Yes, math is a young man's discipline, much like chess! Very impressive, regardless of when you learned it.

 

[chess9]

Duckers: Yes, that is pretty easy, particularly for an engineer since it has a practical application.

 

[InTheClouds]

I guess this is all over my head. Numbers make my head hurt.

 

[Duckers]

ha ha, you are right. Well, I learned something new

 

[Duckers]

ok, I understand this:

(X/30) + (X/40) = 1

Multiply both sides by 1200 which I guess is 30*40

Oh wait, I got it:

(40x+30x) = 1200
therefore x = 1200/70 which is 17.1428571428571428571428571428571

Ha ha, thanks. I forgot how to cross-multiply

 

[Capn]

Duckers I eat problems like those for breakfast. You ever come to my house I'll show you some notebooks from my thermodynamics II class. I'm not much for math theory, but I'm a whiz at a lot of it.

 

[HotLucy]

Hey - Dont read the Singh book about Wiles. I met him a couple of years ago while comleting my doctorate.
Wiles hates the book

 

[chess9]

Lucy: I loved the book! Why doesn't the chap like it?