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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?

PsychoticKiller wrote:
> 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


LOLO, good point

I dunno... didn't they start messing around with the vital statistics on those things a few years ago?

Besides, in this day and age, when any moderately reknowned individual can give toy companies a profit; you can get effigys of just about anyone. I wouldn't be surprised if there was a lolo ferrari doll out there somewhere, and with a pair of...

...teeth that big, she pretty much wipes the floor with Barbie and Cindy. ;)

Is this the demographic of "those too old to play with Barbie dolls?"

Cindy would rock Barbie in a fight anyway

No Ros, you're around the same age as me, and since Miserable has admitted to being in the same demographic - I will now resume my picking on him. Of course, volunteers are always welcome. ;)

This has been a public service announcement brought to you by Babble Inc.™

Pointless Babble wrote:
> Blah. :P
> You any idea how few people around my own age there are here? I'm part
> of wrinkly brigade in comparison to the 15yrs of age standard.


Sorry, I had assumed that you were about 14. I'm 22, if it helps.

I might be older than you. You can pick on me if you want, I don't mind

Miserableman wrote:
> And PointlessBabble, pick on someone your own age

Blah. :P
You any idea how few people around my own age there are here? I'm part of wrinkly brigade in comparison to the 15yrs of age standard.

I picked on Tony once... but then that doesn't really count, coz he tried picking on me first.

I really don't see why I can't just pick on whoever's available for picking on. I mean, Scouse has the whole "internet bully" thing going on, and that pretty much licenses him to do it to anyone. It's just shamefully unfair that I should be singled out due to my differing age range. Equal rights, damn you. :P

The short way is to do it using algebra.

c = circumference of string before lengthening
c' = circumference of string after lengthening
r = radius of string arc before lengthening
r' = radius of string arc after lengthening
n = pi (closest symbol I could find)

It's fair to say:

c = 2nr

and

c' = 2nr'


But, we know that c' = c + 1. Therefore by substitution we get:

c + 1 = 2nr'

2nr + 1 = 2nr'


We also know that the magical difference we're after, x = r' - r. Therefore:

2n(r'-x) + 1 = 2nr'

2nr' - 2nx + 1 = 2nr'


Subtract 2nr' from both sides gives:

-2nx + 1 = 0

2nx = 1


Therefore:

x = 1/(2n)



We have also proved that the gap x does not change with r. x would be 1/(2n) whether the string was originally 1 or 1 million metres long.

sideshow buzz wrote:
> 15.9045cm ? above the surface of the earth

Sideshow Won.... he got it right.

Its ok,
just out of interest what was the short way of doing it?