Driveway

08-30-2002, 08:03 PM

Post your riddles and math/logic problems here

riddle:

Which word in the English language becomes shorter when it is lengthened?

riddle:

Which word in the English language becomes shorter when it is lengthened?

View Full Version : Riddles/Math/Logic

Driveway

08-30-2002, 08:03 PM

Post your riddles and math/logic problems here

riddle:

Which word in the English language becomes shorter when it is lengthened?

riddle:

Which word in the English language becomes shorter when it is lengthened?

moi

08-30-2002, 08:05 PM

short

Driveway

08-30-2002, 08:08 PM

Yea, you got any?

another riddle:

Must Get Here Must Get Here Must Get Here

another riddle:

Must Get Here Must Get Here Must Get Here

MethodMan

08-31-2002, 09:41 AM

3 Mustketeers?

I dont know any riddles.

I dont know any riddles.

Driveway

08-31-2002, 09:43 AM

A barrrel weighs 20 pounds. A man puts something in it, and now it weighs less than 20 pounds What did he put in it.

Nick

08-31-2002, 10:00 AM

A burning match.

Driveway

08-31-2002, 10:04 AM

That good be, but not the answer I'm looking for

jdinger

08-31-2002, 10:19 AM

Oh, I know!

An anti-gravity field modulator!

An anti-gravity field modulator!

Driveway

08-31-2002, 10:23 AM

No

Hint;

Starts with an H

Hint;

Starts with an H

Nick

08-31-2002, 10:24 AM

He but I suppose you would need alot of that for 20lbs.

Jet_Master

08-31-2002, 01:21 PM

a hole. duh

Aran

08-31-2002, 02:30 PM

if a it took a man 5 hours to dig 14 holes, how long would it take him to dig half of a hole?

-KEN-

08-31-2002, 03:31 PM

you can't dig half a hole.

Xterria

08-31-2002, 08:18 PM

approximatly 0.18 hours

really

really

Driveway

08-31-2002, 08:19 PM

Like Ken said, you can't dig half a hole

moi

08-31-2002, 08:23 PM

why not

Driveway

08-31-2002, 08:25 PM

As soon as you take some dirt out it's a whole hole

Aran

08-31-2002, 08:27 PM

yup, that's the right answer ken and drive.

Driveway

08-31-2002, 08:30 PM

See, I'm not completly stupid.

Riddle: (easy one)

The Pope has it but he does not use it. Your father has it but your mother uses it. Nuns do not need it. Your lady friend's husband has it and she uses it. What is it?

Riddle: (easy one)

The Pope has it but he does not use it. Your father has it but your mother uses it. Nuns do not need it. Your lady friend's husband has it and she uses it. What is it?

moi

08-31-2002, 08:45 PM

Originally posted by Driveway

See, I'm not completly stupid.

Riddle: (easy one)

The Pope has it but he does not use it. Your father has it but your mother uses it. Nuns do not need it. Your lady friend's husband has it and she uses it. What is it?

a penis.

See, I'm not completly stupid.

Riddle: (easy one)

The Pope has it but he does not use it. Your father has it but your mother uses it. Nuns do not need it. Your lady friend's husband has it and she uses it. What is it?

a penis.

Driveway

08-31-2002, 08:47 PM

Better than the real answer, but no

BMJ

09-01-2002, 12:25 AM

My riddle: (I gave up on the other one)

A hunter sets out from camp at 4 o'clock in the morning with a compass. According to the compass, he travels due south for 4 hours. At that time he sees a bear and kills it (he is a hunter after all). He drags the bear with him for 4 hours due east, and he takes a quick break. Then he drags the bear due north for 4 hours at which time he arrives back at his camp where he decides he doesn't want the bear after all, packs his SUV and leaves.

So what color was the bear that he killed?

A hunter sets out from camp at 4 o'clock in the morning with a compass. According to the compass, he travels due south for 4 hours. At that time he sees a bear and kills it (he is a hunter after all). He drags the bear with him for 4 hours due east, and he takes a quick break. Then he drags the bear due north for 4 hours at which time he arrives back at his camp where he decides he doesn't want the bear after all, packs his SUV and leaves.

So what color was the bear that he killed?

Driveway

09-01-2002, 06:09 AM

white

golfinguy4

09-01-2002, 01:52 PM

What has been done by every male, except for one? Normally does it with many, but can do it by herself. Is world-renowned for her infinite skill and great noise. And gives many great pleasure.

P.S. You'll probably never get this.

P.S. You'll probably never get this.

rahaydenuk

09-02-2002, 01:54 PM

Well here's a maths one (quite easy):

By considering the series,

1 + t + t^2 + t^3 + ... + t^n

sum the series,

1 + 2t + 3t^2 + 4t^3 + ... + nt^(n-1)

for t not = 1, where a^b denotes a raised to the bth power.

Have fun!

By considering the series,

1 + t + t^2 + t^3 + ... + t^n

sum the series,

1 + 2t + 3t^2 + 4t^3 + ... + nt^(n-1)

for t not = 1, where a^b denotes a raised to the bth power.

Have fun!

Nick

09-02-2002, 10:33 PM

Good problem!

I think it's

(n * t^(n+1) - (n + 1) * t^n + 1) / (t-1)^2

I even sort of proved it.

I think it's

(n * t^(n+1) - (n + 1) * t^n + 1) / (t-1)^2

I even sort of proved it.

rahaydenuk

09-03-2002, 03:17 AM

Originally posted by Nick

Good problem!

I think it's

(n * t^(n+1) - (n + 1) * t^n + 1) / (t-1)^2

I even sort of proved it.

Yeah that's correct, but where's the proof??

Good problem!

I think it's

(n * t^(n+1) - (n + 1) * t^n + 1) / (t-1)^2

I even sort of proved it.

Yeah that's correct, but where's the proof??

Nick

09-03-2002, 08:43 AM

This is how I found the answer

1 + t + t^2 + t^3 + ... + t^n

+ t + t^2 + t^3 + .... + t^n

+ t^2 + t^3 + ... + t^n

+ t^3 + ... + t^n

....

+ t^n

This I proved this was equal to

1 + 2t + 3t^2 + 4t^3 + ... + nt^(n-1)

After that I solved the sums and then used induction

to prove/check the final answer.

1 + t + t^2 + t^3 + ... + t^n

+ t + t^2 + t^3 + .... + t^n

+ t^2 + t^3 + ... + t^n

+ t^3 + ... + t^n

....

+ t^n

This I proved this was equal to

1 + 2t + 3t^2 + 4t^3 + ... + nt^(n-1)

After that I solved the sums and then used induction

to prove/check the final answer.

rahaydenuk

09-03-2002, 09:01 AM

Originally posted by Nick

This is how I found the answer

1 + t + t^2 + t^3 + ... + t^n

+ t + t^2 + t^3 + .... + t^n

+ t^2 + t^3 + ... + t^n

+ t^3 + ... + t^n

....

+ t^n

This I proved this was equal to

1 + 2t + 3t^2 + 4t^3 + ... + nt^(n-1)

After that I solved the sums and then used induction

to prove/check the final answer.

I see, well done, but I have a much shorter proof, using 1 + t + t^2 + t^3 + ... + t^n. Can you/anyone else find it?

You'll kick yourselves...

Good Luck!

This is how I found the answer

1 + t + t^2 + t^3 + ... + t^n

+ t + t^2 + t^3 + .... + t^n

+ t^2 + t^3 + ... + t^n

+ t^3 + ... + t^n

....

+ t^n

This I proved this was equal to

1 + 2t + 3t^2 + 4t^3 + ... + nt^(n-1)

After that I solved the sums and then used induction

to prove/check the final answer.

I see, well done, but I have a much shorter proof, using 1 + t + t^2 + t^3 + ... + t^n. Can you/anyone else find it?

You'll kick yourselves...

Good Luck!

Nick

09-03-2002, 09:30 AM

I noticed that derivative

of 1 + t + t^2 + t^3 + ... + t^n

is the 0 + 1 + 2t + 3t^2 +... + nt^(n-1)

I'm sure you could give a prove or solve it some how

using this?

of 1 + t + t^2 + t^3 + ... + t^n

is the 0 + 1 + 2t + 3t^2 +... + nt^(n-1)

I'm sure you could give a prove or solve it some how

using this?

rahaydenuk

09-03-2002, 09:37 AM

Originally posted by Nick

I noticed that derivative

of 1 + t + t^2 + t^3 + ... + t^n

is the 0 + 1 + 2t + 3t^2 +... + nt^(n-1)

I'm sure you could give a prove or solve it some how

using this?

Exactly! Well done.

If you sum the first series, using the standard geometric series result, you can then differentiate that result to get the sum of the second series, which is the same answer as you got.

Like this:

Summing first series (using standard geometric series result):

1 + t + t^2 + ... + t^n = (1 - t^(n+1))/(1 - t)

d(1 + t + t^2 + ... + t^n)/dt = 1 + 2t + 3t^2 + ... + nt^(n - 1)

Which implies that:

1 + 2t + 3t^2 + ... + nt^(n - 1) = d((1 - t^(n+1))/(1 - t))/dt

= (1 - t^n + nt^(n + 1) - nt^n)/((1 - t)^2)

I think that's quite a nice little solution...

I noticed that derivative

of 1 + t + t^2 + t^3 + ... + t^n

is the 0 + 1 + 2t + 3t^2 +... + nt^(n-1)

I'm sure you could give a prove or solve it some how

using this?

Exactly! Well done.

If you sum the first series, using the standard geometric series result, you can then differentiate that result to get the sum of the second series, which is the same answer as you got.

Like this:

Summing first series (using standard geometric series result):

1 + t + t^2 + ... + t^n = (1 - t^(n+1))/(1 - t)

d(1 + t + t^2 + ... + t^n)/dt = 1 + 2t + 3t^2 + ... + nt^(n - 1)

Which implies that:

1 + 2t + 3t^2 + ... + nt^(n - 1) = d((1 - t^(n+1))/(1 - t))/dt

= (1 - t^n + nt^(n + 1) - nt^n)/((1 - t)^2)

I think that's quite a nice little solution...

Nick

09-03-2002, 10:26 AM

If you havn't got it already check out

concrete mathematic --- A foundation for computer science.

Lots of neat problems, most of them are solved in the back

of book.

I'm trying to read this book in my spare time, but I have

lots of course work so I havn't gotten too far. It's tough

to read.

concrete mathematic --- A foundation for computer science.

Lots of neat problems, most of them are solved in the back

of book.

I'm trying to read this book in my spare time, but I have

lots of course work so I havn't gotten too far. It's tough

to read.

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