A bag contains 3 black marbles and 5 white marbles. Paul picks a marble at random from the bag and replaces it back in the bag. He mixes the marbles in the bag and then picks another marble at random from the bag. Calculate the probability that Paul picks: A. Two black marbles
B. Black marble in his second draw

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm