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.