A lot of 20 bulbs contain 4 defective ones. One bulb is drawn at random from a lot. What is the probability that this bulb is defective?
Total numbers of elementary events are: 20
Let E be the event of drawing defective bulb
The number of defective bulbs in a lot = 4
Then, the favourable outcome =4
∴ P (defective bulb) = P (E) = 4/20 = 1/5