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"Maths problem"

Suspend your disbelief for a moment,

If you tied a length of string around the full circumference of the Earth so it was taught, then made it one metre longer so it floated at a uniform height around the whole Earth, how high would it float? Assume the Earth is a perfect sphere 12,756.3km in diameter.

If you can't work it out, take a guess. Remember that it's a piece of string going around the whole Earth - how high off the ground would it be if you made it 1 metre longer?

This is the long way to solve it:

The diameter, d, of the Earth is 12756300m

:: d = 12756300

The circumference, c, of the Earth, and hence the length of the original string, is d * 3.141 (pi)

:: c = 12756300 * 3.141 = 40067538.3m (40 million metres)


Now we lengthen the string by 1m. The new length of the string shall be called c'

:: c' = 40067538.3 + 1 = 40067539.3

The diameter of the new, longer string c' = pi * d'

:: d' = c' / pi = 40067539.3 / 3.141 = 12756300.31837

Therefore, the difference in diameter, x = d' - d = 12756300.31837 - 12756300 = 0.31837

This is the increase in diameter of the string - we want the radius, which only gives us the height gain on one side.

r = x / 2 = 0.31837 / 2 = 0.159m = 15.9cm



Bar a rounding error, I declare sideshow buzz the winnar! My putting him down earlier was a trick - I believed the answer to be about 30cm, but either is quite incredible when you consider it. Lengthen the circumference of the Earth by just one metre, and its diameter would grow by 15cm.

Well, I thought it was swish (sorry buzz).

I may have to eat humble pie in a second - I only remembered the answer from memory, and working it out on paper now it appears I was a factor of two out and someone here got it (nearly) right. Stay tuned.

And PointlessBabble, pick on someone your own age

Miserableman wrote:
> Here is a plan for you:
>
> 1. Re-read first line of the original post
> 2. Remove head from between buttocks
> 3. Rest of life
>
> You may commence!

There's disbelief, and there's idiocy, what you were proposing was outright idoicy - due to the obvious lacking intellect of whoever thought up the question initially.

So, having addressed "1"...

*Pulls Miserable's head out of his backside*

As for "3", stick in school, and pick up some base knowledge of English grammar. ;)

Pointless Babble wrote:
> Th earth isn't a perfect sphere though... so your question is a bit
> numb. If what you're running an imaginary string around is a perfect
> sphere, then it's not actually the earth, hence your question
> should've been:
>
> "If you took a length of string and wrapped it around a ball then
> gave it 1m of slack, how high above the ball would it float."
>
> The answer is, it wouldn't float, because there'd be nothing holding
> it up - so it would drop to the surface of the sphere, and look pretty
> stupid.
>
> Then if we were to do the same question but for the earth, the answer
> is similar - it wouldn't float, because it would've snapped, due to 1m
> being insufficient slack to stretch the string over the numerous
> mountain ranges on the earth's surface.
>
> *snickers*

Here is a plan for you:

1. Re-read first line of the original post
2. Remove head from between buttocks
3. Rest of life

You may commence!

Th earth isn't a perfect sphere though... so your question is a bit numb. If what you're running an imaginary string around is a perfect sphere, then it's not actually the earth, hence your question should've been:

"If you took a length of string and wrapped it around a ball then gave it 1m of slack, how high above the ball would it float."

The answer is, it wouldn't float, because there'd be nothing holding it up - so it would drop to the surface of the sphere, and look pretty stupid.

Then if we were to do the same question but for the earth, the answer is similar - it wouldn't float, because it would've snapped, due to 1m being insufficient slack to stretch the string over the numerous mountain ranges on the earth's surface.

*snickers*

bah my maths must be off tonight (might be slightly alcohol related)

There's a long way to solve this and a short way. By the looks of things, you're all trying the long way and getting muddle somewhere.

Miserableman wrote:
> My A-level teacher asked the class this when we were 17 (5 years ago -
> b****r), so it's probably unfair to ask people any younger. They can
> still guess though.
>
> We thought the answer was quite suprising, and so did his wife, who
> refuses to believe it to this day |o/

its still very hard to Awnser... can you tell us the formula? :)

My A-level teacher asked the class this when we were 17 (5 years ago - b****r), so it's probably unfair to ask people any younger. They can still guess though.

We thought the answer was quite suprising, and so did his wife, who refuses to believe it to this day |o/

make the voices stop wrote:
> How are you people Guessing these numbers?
> freaks.
>
> too much math for my brain cells..math is evil

YOU HAVE BRAIN CELLS! :O :O :O