A box contains 12 resistors, three of which are defective. If four are selected, find the probability of getting one defective resistor.

Answer 1

prob(defective) = 3/12 = 1/4
prob(not defective) = 3/4

prob(getting 1 defective when 4 selected)
= C(4,1)(1/4)(3/4)^3
= 4(1/4)(27/64)
= 27/64