Solution:
Total number of screws = 600
Number of possible outcomes = 600
Number of rusted screws = one tenth of 600
= (1/10)×600 = 60
Number of remaining good screws = 600-60 = 540
Number of favourable outcomes = 540
Probability of a good screw, P(E)
P(E) = 540/600 = 54/60 = 9/10
Hence the required probability is 9/10.