Question

In a box containing 100 are defective. The probability that out of a sample of 5 bulbs, none is defective is :

(i) (1/2)⁵

(ii) 10^-1

(iii) 9/10

(iv) (9/10)⁵

Answer 1

Answer is  (iv)

Number of bulbs in box = 100 

Number of defective bulbs = 10 

∴ Probability of defective bulbs = 10/100 = 1/10

∴ So probability of non defective bulb = 1 – 1/10 = 9/10

∴ Probability that no bulb is defective out a sample of 5