The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Math Topics » geometry.puzzles

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Cable around the Equator
Replies: 10   Last Post: Jun 17, 2012 2:29 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]

Posts: 4
Registered: 12/10/04
Re: Cable around the Equator
Posted: Nov 5, 1996 9:37 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

How can adding 50' of slack to the cable spread evenly around the equator
add 8' at each point? Your math was impeccable but your answer does not
pass the sanity check! This is why we must not blindly accept mathematical
results. That is the lesson to be learned from this geometry problem. wrote in article
> On Mon, 4 Nov 1996, mfr1 wrote:

> > Ma Bell wants to place a telephone cable around the equator. She adds
> > feet to the length of the cable beyond what is required. This slack in
> > cable allows the cable to be strung up above the ground. How high up
> > the surface of the earth will the cable stand? You can assume that the
> > earth is a perfect sphere.
> >
> > In your mind, run a sanity check on your answer to see if it makes

> >
> Surprisingly, you will be able to walk under the cble easilty. Since the

> circumference of a circle is C = 2piR, each increase in R obf 1 foot
> increases the circumference by 2pi feet. since the cable has been
> increased by 50 feet the radius of the cable-circle will be increased by
> 50/2pi or about 8 feet!
> Alan Lipp

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.