a machine made some bolt in which 75% bolt are waste , if 5 bolt are choose then find probability to come max. 2 waste bolt
((5c0 + 5c1 + 5c2)/(2*2*2*2"2))*3/4
Sum of 0 waste bolt + 1 waste bolt+ 2 waste bolt divided by number of total outcomes multiply by the number of waste bolt made in machine.