Answer:
3.33% probability that both pens are defective.
Step-by-step explanation:
The pens are chosen without replacement, so we use the hypergeometric distribution to solve this question.
Hypergeometric distribution:
The probability of x sucesses is given by the following formula:
In which:
x is the number of sucesses.
N is the size of the population.
n is the size of the sample.
k is the total number of desired outcomes.
Combinations formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.
In this question:
2 defective, so x = 2.
25 pens, so N = 25.
Two pens will be selected, so n = 2.
5 are defective, so k = 5.
3.33% probability that both pens are defective.