20. sampling a customer at cavallaro's fruit stand picks a sample of 3 oranges at random from a crate containing 60 oranges, of which 4 are rotten. what is the probability that the sample contains 1 or more rotten oranges?

19%

Step-by-step explanation:

First, let's notice that having 1 or more rotten oranges in the sample is the complement of having 0 rotten oranges in the sample. That means

proba (1 or more rotten oranges) + proba (0 rotten oranges) = 100%

We will focus in the case of 0 rotten oranges that's easier and then we go back to this last equation.

For 0 rotten oranges, we need that the customer picks 3 good oranges. As there are 4 rotten oranges in the crate of 60, we have good oranges.  

So, the customer has a 56/60 chance of getting a good orange. As he needs 3 good oranges at the same time, he has chance.

Therefore,  proba(0 rotten oranges) = = 81% (approximately)

Going back to the first paragraph, we have proba(1 or more rotten oranges) = 100% - proba(0 rotten oranges) = 100% - 81% = 19%