Combination and Permutation

Permutation means when the order is important. You use this formula: nPr=n!/(n-r)! Combination means when the order is not important. You use this formula:Cr=n!/(n-r)!r! Example 1: 5people are standing in a line.  How many different outcomes are possible?   P(5, 5) = 5! = 5 × 4 × 3 × 2 × 1 = 120 Example 2:  In how many ways can you select a committee of 4 people from a group of 10 members? C(10, 4) = 210 Example 3: License plates for cars have to be unique. If a license plate contains 6 characters consisting of 2 letters followed by 4 digits  example:  QW2354,  A-how many different license are possible? B-how many different license are possible if letters were allowed to repeated but numbers are not allowed to be repeated? There are 26 × 26 × 10 × 9 × 8 × 7 =  3,407,040 different plates with no repeating numbers. Example 4: In how many ways can you select a committee of 3 people from a group of 12 members? C(12, 3) = 220