## Solution to: Men on the Moon

The moon's diameter is not needed to solve this problem!
Let the moon's radius be *r* meters.
Then the length of the cable is 2×*pi*×*r*-1 meters.
Let the depth of the groove be *x* meters.
2×*pi*×(*r*-*x*) must be equal to 2×*pi*×*r*-1.
Solving the equation 2×*pi*×(*r*-*x*)=2×*pi*×*r*-1 gives *x* = 1/(2×*pi*) meters (about 0.159 meters).

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