Question

A certain lot consisting of ten items has three defective items and seven nondefective items. How many possible subsets of 2 items can be chosen from this lot?

21
45
90

Answer 1

45

Explanation:

Answer 2

45

Explanation:

The order in which the items are chosen is not important. So we use the combinations formula to solve this question.

Combinations formula:

`C_(n,x)` is the number of different combinations of x objects from a set of n elements, given by the following formula.

`C_(n,x) = (n!)/(x!(n-x)!)`

How many possible subsets of 2 items can be chosen from this lot?

Combinations of 2 from a set of 10. So

`C_(10,2) = (10!)/(2!(10-2)!) = 45`