Question 970092
Probability of 2 defective resistors.

There are 6 possible ways: first and second, first and third, first and fourth, second and third, second and fourth, third and fourth.

Look at the first two.

(3/12)*(2/11)*(9/10)*(8/9)
(3/12)*(9/11)*(2/10)*(8/9)

Notice, that each of these has the same product in the numerator and in the denominator.  They aren't necessarily matched with the same denominator.  Therefore, take the product of one of these and multiply by 6.

(432)*6/11880

= 2592/11880
P=0.2181 or P=0.22