Discussion » Questions » Math » If a piece of string was tied around the Earth's equator, and another piece of string was floated 6 inches away all the way around
Benedict Arnold

If a piece of string was tied around the Earth's equator, and another piece of string was floated 6 inches away all the way around

How much longer would the outer piece of string be than the inner piece?

It is easier than you think to work out

Clue - You would arrive at the same solution if you used a golf ball instead of the planet Earth

Scroll down for answer

ro - ri x π

= 6” x π

= 18.85”

Posted - June 28, 2016
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Responses


  • 11107

    The outer piece of string would be 307.452 miles longer. Cheers!

      June 28, 2016 7:57 AM MDT
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  • Bez

    2148

    Huh?

      June 28, 2016 7:58 AM MDT
    0

  • 3719
    Another way to express it:

    If we call the diameter of the Earth, E, inches.

    Then the string on the surface is π.E inches long.

    So the floating string's length is π (E + 12) inches (the 6" is the radius difference so the diameter difference is 12").

    Therefore the circumference = ( πE + π12 ).

    Hence the floating string is π12 inches longer, or 37.704 inches.

    Not very much at all given that the planet is roughly 8000 miles in diameter! This post was edited by Durdle at October 4, 2016 5:28 PM MDT
      October 4, 2016 5:28 PM MDT
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