1-24 Counting These exercises involve counting.

Test Questions If you must answer only eight of ten questions on a test, how many ways do you have of choosing the questions you will omit?

To find:

The number of ways of choosing a question that will be omitted.

Approach:

A combination of r objects from a set is any subset of the set that contains r elements (without regard to order).

If a set has n objects, then the number of combination of r elements from the set is denoted C(n,r) and is called the number of combination of n objects taken r at a time.

C(n,r)=n!r!(n−r)!……(1)

Calculation:

Substitute 10 for n and 2 for r in equation (1)