Permutations

The first instance of  is under the Probability and statistics Math Mission. This exercise practices the concept of a permutation.

Types of Problems
There are two types of problems in this exercise:


 * 1) Rearrange the letters: This problem asks how many different ways the letters in a word can be rearranged. The student figure out how many ways this is possible, and answers in the available spot.Perm1.png
 * 2) Put in a row: This problem asks in how many ways a subset of a given set of objects can be arranged in a row. The student figures out the answer and puts it in the available position.Perm2.png

Strategies
This exercise is easy to get accuracy and speed badges because the problems are extremely consistent with the exception of the numbers.


 * 1) The formula for picking r items from a collection of n is: $$n!/(n-r)!$$.
 * 2) When rearranging all the letters from a word (with no repeated letters as these seem to be) the answer is the factorial of the number of letters in the word.
 * 3) The multiplication principle can be used to solve the problems in this particular exercise.
 * 4) Some common factorials: $$5!=120, 4!=24, 3!=6, 2!=1, 1!=1, 0!=1$$.