flagpole puzzle

MattcAnderson · 2014-09-29, 23:10

Hi Math people,

I have a fun puzzle for you today.

Two flagpoles are each 100 feet high. A rope 150 feet long is strung between the tops of the flagpoles. At its lowest point the rope sags to within 25 feet of the ground. How far apart are the flagpoles?

Regards,
Matt

Batalov · 2014-09-29, 23:21

Well, it would have been a hell of a problem (with knowing the chain curve's formula, which is cosh(), and knowing how to integrate the sqrt(1+f'²))... but there's only enough rope to be simply folded together twice 75 ft. The flagpoles are zero ft apart..

MattcAnderson · 2014-09-30, 05:01

Batalov is right. Most people don't know about the mathematical curve that is the Catenary and equivalently hyperbolic cosine.
http://en.wikipedia.org/wiki/Catenary

Maybe some others would like to chime in on this one.

Regards,
Matt

MattcAnderson · 2014-09-30, 17:18

Hi math people,

I have attached an answer page for the flagpole challenge.

Regards,
Matt

ewmayer · 2014-09-30, 21:14

I was presented this same one on a paper napkin by a would-be stump-the-math-geek-er back in college - I believe it is designed to confuse those who *are* familiar with catenaries and such, by getting one to bog oneself down in the maths, thus missing the "trivial catenary" no-maths-other-than-division-by-2-required answer.

(And yes, I did quickly get the "null result" way back when.)

But, did we really need a "answer page" for this?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Some puzzle	Harrywill	Puzzles	4	2017-05-03 05:10
Four 1's puzzle	Uncwilly	Puzzles	75	2012-06-12 13:42
4 4s puzzle	henryzz	Puzzles	4	2007-09-23 07:31
Dot puzzle	nibble4bits	Puzzles	37	2006-02-27 09:35
now HERE'S a puzzle.	Orgasmic Troll	Puzzles	6	2005-12-08 07:19

2014-09-29, 23:21	#2
Batalov "Serge" Mar 2008 Phi(4,2^7658614+1)/2 3⁶×13 Posts	Well, it would have been a hell of a problem (with knowing the chain curve's formula, which is cosh(), and knowing how to integrate the sqrt(1+f'²))... but there's only enough rope to be simply folded together twice 75 ft. The flagpoles are zero ft apart..

2014-09-30, 05:01	#3
MattcAnderson "Matthew Anderson" Dec 2010 Oregon, USA 2⁵·5² Posts	Batalov is right. Most people don't know about the mathematical curve that is the Catenary and equivalently hyperbolic cosine. http://en.wikipedia.org/wiki/Catenary Maybe some others would like to chime in on this one. Regards, Matt

2014-09-30, 21:14	#5
ewmayer ∂²ω=0 Sep 2002 República de California 103×113 Posts	I was presented this same one on a paper napkin by a would-be stump-the-math-geek-er back in college - I believe it is designed to confuse those who are familiar with catenaries and such, by getting one to bog oneself down in the maths, thus missing the "trivial catenary" no-maths-other-than-division-by-2-required answer. (And yes, I did quickly get the "null result" way back when.) But, did we really need a "answer page" for this?