A Belt Around Two Pulleys

  1. Given two pulleys of radius (X) and (Y), and the distance (D) between their centers, find the circumference (Z) of the belt which goes around both pulleys. Assume the belt touches at least part of each pulley, and the pulleys can overlap (D can be less than X+Y).
  2. With the definitions as above, if you're given X, Y, and Z, find D.
Source: Reader David Quinn, though I wouldn't be surprised to hear of other sources.
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