Question

Of the 20 flash bulbs in a box, 2 are defective. an inspector will select 2 light bulbs simultaneously and at random from the box. what is the probability that neither of the light bulbs selected will be defective

Answer 1

`|\Omega|=C(20,2)=(20!)/(2!18!)=(19\cdot20)/(2)=190\\ |A|=C(18,2)=(18!)/(2!16!)=(17\cdot18)/(2)=153\\\\ P(A)=(153)/(190)\approx81\%`