Question 1132411
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I will assume that the problem is about 12 transistors, of which 3 are defective....<br>
P(3 defective) = {{{(C(3,3)*C(9,0))/C(12,3) = (1*1)/220 = 1/220}}}<br>
P(0 defective) = {{{(c(3,0)*C(9,3))/C(12,3) = (1*84)/220 = 84/220 = 21/55}}}<br>
Another simple way to calculate the probabilities in this problem is to calculate the probabilities when choosing the transistors one at a time:<br>
P(3 defective) = {{{(3/12)*(2/11)*(1/10) = 6/1320 = 1/220}}}<br>
P(0 defective) = {{{(9/12)*(8/11)*(7/10) = 504/1320 = 21/55}}}