971. In the group of athletes 20 skiers, 6 cyclists and 4 runners. The probability to fulfill the norm is as follows: for a skier, 0.9; for a bicyclist of 0.8 and for a runner of 0.75. Find the probability that an athlete, chosen at random, will fulfill the norm.

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)