21.

Counting numbers are to be formed using only the digits 7, 5, 1, 2, 9, 6, and 3. Determine the number of different possibilities for two-digit numbers. numbers (Simplify your answer. Type a whole number.)Use permutations, combinations, the fundamental counting principle, or other counting methods, as appropriate. In how many ways can a class of sixteen students be divided into three sets so that four students are in the first set, five students are in the second, and seven are in the third? The group of students could be divided into the three sets ways. (Type a whole number.)How many different three-number "combinations" are possible on a combination lock having 32 numbers on its dial? (Hint: "Combination" is a misleading name for these locks since repetitions are allowed and order makes a difference.) There are different "combinations." (Type a whole number.)A Civil Air Patrol unit of fourteen members includes four officers. In how many ways can three members be selected for a search and rescue mission such that at least one officer is included? The number of ways is . (Simplify your answer.)