Math CentralQuandaries & Queries


Question from fikile, a parent:

By how much must an equatorial cable be extended in order that it runs 1meter above the ground?


The circumference of a circle of radius $r$ units is $2 \times \pi \times r$ units.

Suppose the radius of the Earth is $r$ meters. What is the circumference?

If you extend the cable so that it is $1$ meter above the surface then the radius of the circular cable is $r + 1$ meters. What is its circumference?

Write down the difference of the two circumferences and simplify.


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