Question

suppose 100 refrigerator were manufactured during a day. ninety five operated perfectly and 5 had at least one defect. a sample of four is selected at random

Answer 1

Solution:

Total no. of refrigerators=100

No. of refrigerators operated perfectly=95

No. of defective refrigerators=5

No. of selected refrigerators=4

To find the probability that all 4 selected operated perfectly.

Required probability$=\dfrac{^{95}C_4}{^{100}C_4}=0.812$