Question 1174700
there are 15 items in the box.
4 of them are defective.
11 of them are not.


the probability that the first item you pick out of the box is not defective is 11/15.


assuming the first item you picked out of the box was not defective, then the box now contains 14 items.
4 of them are defective.
10 of them are not.


the probability that the second item you pick out of the box is defective is 4/14.


assuming the second items you picked out of the box was defective, then the box now contains 13 items.
3 of them are defective.
10 of them are not.


the probability that the third item you pick out of the box is not defective is 10/13.


the probability that all 3 events occur is:


11/15 * 4/14 * 10/13 =  (11*4*10) / (15*14*13) = 440 / 2730 = 4.1611721612.