Question 169882
A box contains 74 brass washer, 86 steel washers and 40 aluminium washers. Three washers are drawn at random from the box without replacement. 
a) Determine the probability that all three are steel washers.
# of ways to succeed = 86C3
# of possible outcomes = 200C3
P(success) = 86C3/200C3 = 0.0779...
------------------------------------------------- 
b) Determine the probability that there are no aluminium washers drawn, when three washers are drawn at random from the box without replacement.
# of ways to succed = 114C3/200C2
-------------------------------------------------- 
c) Find the probability that there are two brass washers and either a steel or an aluminium washer when three are drawn at random, without replacement.
# of ways to succeed: 
Draw to brass washers in 74C2 ways
Draw a steel or aluminum washer 126 ways
Total # of ways to succeed 74C2*126 
Prob of success: [74C2*126]/[200C3] = 0.25912
=========================
Cheers,
Stan H.