A piece of string is stretched tightly around the Earth along its equator. Imagine that this string along the equator forms a perfect circle, and imagine that to reach around that perfect circle, the string has to be exactly 25,000 miles long. Now imagine that you wanted to suspend this string 4 inches above the surface of the Earth, all the way around it. How much longer would the string have to be do do this?

Before you visit my blog to read any further, guess the answer. How much longer would the string have to be? A few inches? Several miles? What do you think?

## 7 Comments

Florin

30/03/2012

The string should be 8 X pi inches longer, that is about 24-25 inches longer. Apparenly it has nothing to do with how long the string is :-)

Arya

02/04/2012

Π * d = 25000

Π * (d+8) - Π * d = x(say)

Π * d + Π * 8 - Π * d = x

Π * 8 = x

x = 3.14 * 8 = 25.12

Arya

02/04/2012

&Pi * d = 25000

&Pi * (d+8) - &Pi * d = x (say)

&Pi * d + &Pi * 8 - &Pi * d = x

&Pi * 8 = x

x = 3.14 * 8 = 25.12

Ian

02/04/2012

I reckon 33 miles, 52 yards , 3.45 inches. Roughly.

Dzavid

18/04/2012

a few inches because O = 2 * r * 3.14 i.e. 2 * delta R * 3.14 = 2 * 4 * 3.14 = 25.15

Sukanta

14/08/2012

Current Circumference in inches

= 25000*63360

= 1584000000.00 inches

Current Radius

= 1584000000.00/2*3.14

= 252229299.36

New Radius

= 252229299.36 + 4

= 252229303.36

New Circumference

= 2*3.14* 252229303.36

= 1584000025.12 inches

Difference +25.12 inches

Girish Singhal

07/08/2014

The answer should be calculated keeping in mind the different units that are mentioned for given figures!

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