Question:
Refer to Q. 29. The probability that bulbs selected randomly from the lot has life less than 900 h, is
(a) 11/40
(b) 5/16
(c) 7/16
(d) 9/16
Solution:
(d) Total number of bulbs in a lot, n(S) = 80
Number of bulbs whose life time is less than 900 h, n(E) = 10 + 12 + 23 = 45
Probability that bulbs has life time less than 900 h =n(E)/n(S) = 45/80 = 9/16
Hence, the probability that bulb has life time less than 900 is 9/16.