Probability: Permutations & Combinations

Front

What is a permutation?

Back

A permutation is an arrangement of objects in a specific order. The number of permutations of n objects taken r at a time is given by n! / (n - r)!.

Front

What is a combination?

Back

A combination is a selection of objects without regard to the order. The number of combinations of n objects taken r at a time is given by n! / (r! * (n - r)!).

Front

Calculate 12P4.

Back

12P4 = 12! / (12 - 4)! = 11880.

Front

What is the formula for permutations?

Back

The formula for permutations is nPr = n! / (n - r)!.

Front

What is the formula for combinations?

Back

The formula for combinations is nCr = n! / (r! * (n - r)!).

Front

If you have 5 cards to choose from a deck of 52, what is r?

Back

r = 5.

Front

How many ways can a disc jockey choose and arrange 3 songs from 9 songs?

Back

The number of ways is 9P3 = 9! / (9 - 3)! = 504.

Front

How many ways can a coach choose 5 starting players from 11 players?

Back

The number of ways is 11C5 = 462.

Front

How many ways can 8 cheerleaders be chosen for 3 positions?

Back

The number of ways is 8P3 = 8! / (8 - 3)! = 336.

Front

What is the difference between permutations and combinations?

Back

Permutations consider the order of selection, while combinations do not.