Question

The crew of an airplane AN-12 consisted of a pilot, co-pilot, and a mechanic. Suppose that 12 aviators and 4 mechanics were trained. How many different crews can they assemble?

Answer 1

The number of permutations of the 12 aviators taken two at a time is given by:
\[\large P(12, 2)=\frac{12!}{(12-2)!}=12\times11\]
Each of these permutations can be combined with one of the 4 different mechanics, giving a total of:
\[\large 12\times11\times4=(you\ can\ calculate)\ crews\]