how long's a piece of string?

Question

imagine the earth is perfectly round.You tie a piece of string around it so that it touches all the way around. How much string would you have to add so that the string was exactly half an inch away from the surface all the way around?Please explain>

good one teaser.!0 points.I still question the answer though I know its correct!

string represents circumference,which in turn is Pi x diameter.New circum'=Pi x new diameter which is 1 inch longer.so answer is Pi x[new diameter-old diameter]which is Pi[3.14 x1] = 3.14 inches

Answer 1

3.14 inch !! Surprised No? Here is te answer, when we tie apiece of string around the earth so that it touches all the way around means , we are calculating the circumference of the cross section of the earth.

Let R be the radius of the cross section which is a circle, then coircumference will be

2(Pie)R

Now to get the string 1/2 an inch away from the surface, we need to increase the radius by 1/2 an inch, Thus the new circum ference will be

2(pie) x(R+1/2)

= 2(Pie)R + 2(Pie)/2

=2(Pie) R + Pie

Difference in the new circumference and old will be the difference in the length of the string which will be equal to

2(Pie)R + Pie -2(Pie)R = Pie


and value of Pie is 22/7 =3.14, Since we have taken inch as our Unit, Answer will be 3.14 inches more string would be required.

Answer 2

Very interesting.....

Facts: The diameter of the earth at the equator is greater than the diameter at the poles. There is a slight bulge at the equator.This is known as an ellipsoid.

Now the diameter of the earth at the equator is 7926.41 miles or 12756.32km

The diameter of the earth at the poles is 7901 miles or 12715.43km.

Let the length of the string be equal to the circumference of the earth at the cross section...

Circumference of a circle is equal to 2pi r or pi d where pi is 22/7.

If the string is 1/2 inch away from the earth around, it means that the diameter is extended by a total of 1 inch around.

Conversion....

1 inch is equal to 2.54 cm.
If we are working in km, the diameter at the equator now becomes

12756.32km + 2.54cm.. or (12756.32 +0.0000254) km

=12756.3200254 km.

If circumference of a circle is equal to pi d, where d is the diameter,

then the circumference is equal to

12756.3200254 * 22/7

= 40091.2915084 km

or 40,091.30 km at the equator. = length of string......

Do the same using diameter at the poles for the circumference.

Answer 3

This Is Neither A Joke Or A Riddle As Asked. Might I Suggest You Ask It Again In Mathematics Or Geometry Category. You Might Get A Closer Answer There. Sorry I Don't Have My Maths Head On Today. Good Luck With The Answer.

Answer 4

12,755.7 kms (diameter of the earth) x 1000 = 12755697.37

metres, x 100 = 1275569737 cms + 2.54cms(half inch & half inch

on other side) = 1275569740 x 3.141592(Pi) = 4,007,319,689

cms....then just take away the two...

well I know how to work it out, but the answer may be slightly

off because the figure I started with must have been rounded

up...thanks...it was good to use some maths again to do

something interesting.

Answer 5

a bite of string is going right into a pub an sits down. The bartender says you ought to pass away we dont serve string right here. The string is going out to the line and asks a guy to tie him in a knot. the guy does it yet as he ties the knot the ends of the string grow to be frayed. The string says thats ok and walks returned into the pub a sits down. The bartender says, are not you that piece of string I kicked out of right here previously. The string says no i'm a frayed knot.

Answer 6

http://geography.about.com/library/faq/blqzdiameter.htm
the diameter of the earth from the above link
length of string = inside diameter of the earth divided by half an inch times 3.14
7926.41 miles divided by half an inch multiplied by 3.14

add 577161390.464 inches to get the half inch distance from the earth

which is an extra 9,109.23912 miles of string at the equator

Answer 7

3.14 Inches.
If you add one foot to the radius, circumference increases by 2pi feet. If you add one inch to the radius, circumference increases by 2pi inches. It works for all circles.
Another way to look at it ...
25,000 x 5280 feet / 2pi = radius of earth in feet
((25,000 x 5280 feet)) + 6 feet) / 2pi = new radius ... then subtract one from the other.

Answer 8

measure the piece of string that has gone round the world divide by pye 3.14 then add the the half inch then multiply by 3.14

Answer 9

as long as u want it to be!
Try this:
Get a globe, put a string around it, end to end! On the globe it would say : how much its been scaled down to, then just multiply the string measurement with the scaled down figure and u have your answer!

Answer 10

First go and get a string so long