# Annulus - problems

- The coil

How many ropes (the diameter 8 mm) fit on the coil (threads are wrapped close together) The coil has dimension: the inner diameter 400mm, the outside diameter 800mm and the length of the coil is 470mm - Shooter

The probability that a good shooter hits the center of the target circle I is 0.21. The probability that the target hit intercircle is II 0.36. What is the probability that it hits the target circle I or II?

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