Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

#51 2010-03-11 14:00:18

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Yes, that B guy is the only person in the civilized world who didn't see that you just have to square 1 / x^2. What a dummy.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#52 2010-03-15 20:35:17

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi;

Moderate to difficult:

Six ducks are swimming in a pond. You are a duck hunter. Each duck can be hit with probability d / 15 where d is the number of unhit ducks. What is the average number of shots required to hit every duck. You have 30 shells, you are wondering whether that is enough. You ask the experts:

A says) 30 is plenty.
B says) Get more cause you will run out.
C says) Wow! 30 is exactly right.
D says) The question is too difficult to answer.

Who is right?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#53 2010-03-16 06:10:17

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Is this cool with you?


Why did the vector cross the road?
It wanted to be normal.

Offline

#54 2010-03-16 20:47:33

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi mathsyperson;

That's correct. Can anybody say what the average number of shots will be?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#55 2010-03-20 00:53:08

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

12 black balls are to be distributed into 5 bowls:


Which do you like?



12 black balls are to be distributed into 5 bowls each of which must have at least one black ball

What do you think?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#56 2010-03-25 20:19:40

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi;

This one should get thousands of correct replies.

The sum of 11 numbers is 91. The sum of the first 6 is 61. the sum of the last 6 is 52. The 2 smaller lists have 1 number in common, what is it?

A says) No way can this be done.

B says) This is easy and I can prove it.

C says) You can get it but only using a computer.

Hide your answer and support it.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#57 2010-03-26 22:41:13

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Is this cool with you?


Why did the vector cross the road?
It wanted to be normal.

Offline

#58 2010-03-26 22:57:31

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi mathsyperson;

That's correct. Good work.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#59 2010-03-27 13:34:24

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 3,915

Re: Is this cool with you?


"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

Offline

#60 2010-03-27 14:04:50

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Ok mathsyperson and phrontister;

Both answers are right but they are both way too short.
It doesn't even look like you did any work. If you want full credit your methods must be fuller, more authoritative, beefier, puffier. Let me demonstrate.

See, beefier, puffier. The trick is to make simple problems look difficult.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#61 2010-03-27 14:30:10

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 3,915

Re: Is this cool with you?

Hi Bobby,

Granted, your solution is much more impressive-looking than ours and any astute examiner would be bowled over by the obvious amount of thought that went into that construction. It's just a pity you'd only get maximum credit for it, and not more.

beefier: fatter.
I didn't know this until now, and I'm digressing badly here, but beef-brained means thick-headed.

puffier: containing more puff.
Probably related to pollyspeak.

Last edited by phrontister (2010-03-27 14:33:37)


"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

Offline

#62 2010-03-27 14:42:30

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

phrontister wrote:

but beef-brained means thick-headed

True enough, all this talk about beef and brains is making me hungry.

A wonderful poster on another forum who is as brilliant as she is charming gave me an interesting idea for another problem:

You have a list of n elements that are integers. You need to know the maximum element in the list. You are not allowed to compare elements with a <, >.  You are not allowed to sort the list. Remember eyeballing the list is a compare. How would you find the maximum value?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#63 2010-03-27 23:16:25

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Is this cool with you?

It depends on exactly what you're allowed to do.

One way would be to subtract one from every element in the list, and keep doing so until only one of the elements is positive. (Or if they all start non-positive, add one to each element until one of them becomes positive)


Why did the vector cross the road?
It wanted to be normal.

Offline

#64 2010-03-28 09:05:43

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi mathsyperson;

I see two problems with that idea. If you decrement each element by one and you started with all positive elements you will have to compare the elements ( to 0 ) sooner or later which is not allowed. Also you have the problem of figuring out whether to increment or decrement. What if the list contains both positve and negative integers?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#65 2010-03-28 09:24:29

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Is this cool with you?

Yeah, I thought that might be considered cheating.
"No officer, I wasn't comparing, I was just checking for minus signs! Honest!"

The other one's not a problem though. You increment the numbers iff they are all non-positive.
If any of them are positive, you decrement instead.


Why did the vector cross the road?
It wanted to be normal.

Offline

#66 2010-03-28 10:39:19

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi mathsyperson;

That would be okay if we knew something about the elements of the list, but you don't.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#67 2010-04-03 13:26:32

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi;

Easy one:

sleep-anim-male-sleep-sleeping-smiley-emoticon-000368-medium.gif

How many integers don't have a zero and sum to at most 8?


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#68 2010-04-03 21:25:15

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Is this cool with you?

After thinking more about my suggestion, if you were allowed to check for positivity of numbers then it'd be fairly trivial. a < b iff a-b < 0, etc.

This would work though:


Why did the vector cross the road?
It wanted to be normal.

Offline

#69 2010-04-03 23:22:53

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi mathsyperson;

I walked through your code with some small examples and that idea seems okay. I am not an expert on Matlab so... Presumably you have tested it exhaustively already. Good work!


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#70 2010-04-04 00:10:13

ZHero
Real Member
Registered: 2008-06-08
Posts: 1,889

Re: Is this cool with you?

bobbym wrote:

hey!! these Exactly were the formulas i was looking for in this post!!
i had come across the same set of formulas somewhere in the forum long ago but was not able to find it again....
dizzy
thx!!


If two or more thoughts intersect with each other, then there has to be a point.

Offline

#71 2010-04-04 01:17:12

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: Is this cool with you?

I just put code there because I thought it was a good way to explain my idea.
Hopefully even if you don't know MATLAB you can see what I'm trying to do.

That idea is much quicker, but it uses the abs function which could be considered cheating.


Why did the vector cross the road?
It wanted to be normal.

Offline

#72 2010-04-04 01:29:53

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi mathsyperson;

That idea is much quicker, but it uses the abs function which could be considered cheating.

Not really, you only couldn't use < and >.

I created the recursive idea because her two relationships ( max2 and max3 ) just seemed to suggest it. If I were doing it I would use your procedural approach over recursion.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#73 2010-04-08 20:49:41

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi;

Easy:

What is the remainder of

When it is divided by 9?

A says) 2

B says) 5

C says) 1

Justify your answer and please hide it.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

#74 2010-04-08 21:41:02

ZHero
Real Member
Registered: 2008-06-08
Posts: 1,889

Re: Is this cool with you?

bobbym wrote:

Hi;

Easy:

What is the remainder of

A says) 2

B says) 5

C says) 1

Justify your answer and please hide it.

Remainder, i suppose, is used in context of Division right???
Shouldn't it be...
What is the remainder of


divided by .......???   what


If two or more thoughts intersect with each other, then there has to be a point.

Offline

#75 2010-04-08 21:50:48

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,672

Re: Is this cool with you?

Hi ZHero;

Sorry, can't even copy my own problem correctly. I have fixed the original post.

Easy:

What is the remainder of

When it is divided by 9?

A says) 2

B says) 5

C says) 1

Justify your answer and please hide it.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

Offline

Board footer

Powered by FluxBB