Question 1153795
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washers, not watchers....!<br>
Number of ways of choosing 3 of the total 160 washers: C(160,3) = 669920<br>
Number of ways of choosing 3 that are not aluminum -- i.e., choosing 3 of the 120 washers that are not aluminum: C(120,3) = 280840<br>
Probability of choosing 3 of which none are aluminum:<br>
280840/669920 = .4192142345<br>
...OR...<br>
P(1st is not aluminum) = 120/160 = 3/4
P(2nd is not aluminum) = 119/159
P(3rd is not aluminum) = 118/158 = 59/79<br>
P(all 3 are not aluminum) = (3/4)(119/59)(59/79) = 21063/50244 = .4192142345<br>