A factory produces bulbs. The probability that any one bulb is defective is 1/50 and they are packed in boxes of 10. From a single box, find the probability that

(i) none of the bulbs is defective


(ii) exactly two bulbs are defective


(iii) more than 8 bulbs work properly

Let X is the random variable which denotes that a bulb is defective.


Also, n =10, and


(i)None of the bulbs is defective i.e., r=0



(ii)Exactly two bulbs are defective i.e., r=2





(iii)More than 8 bulbs work properly i.e., there is less than 2 bulbs which are defective.


So, r<2 r=0,1


∴P(X=r) =P(r<2) =P (0) +P (1)


=+




31