Question

A box contains ninety good and ten defective screws. If ten screws are used, what is the probability that none is defective

Answer 1

The total amount of screws in the box is: 90+10 = 100.

The number of ways to select 10 screws from 100 is: N = (C100)^10.

The number of ways to select 10 screws from good ones is: m = (C90)^10.

Thus, the probability of taking 10 good screws is: P = m/N = ((C90)^10)/((C100)^10) = (90!*90!)/(80!*100!) ≈ 0.33

Explanation: