Permutation land Combination

Sooooooooooo this week we learned Coach Matt taught us about permutation and combination:

-With permutation the order is important. Formula: nPr = n!/(n-r)!
-With combination the order isn't important. Formula: nCr = n!/(n-r)!r!

Example 1: How many 2 digit numbers can you make using digits 1, 2, 3, and 4 withour repeating the digits?

Since you don't want to repeat the order is important so you need to use permutation. 4P2 = 4!/(4-2)! = 12

Example 2: We need to form a 5 a side team in a class of 12 students. How many diffent teams can be formed?

Since the order isn't important you use combination. 12C5 = 12!/(12-5)!5! = 792

Example 3: How many 6 letter words can we make using the word LIBERTY without repitition?

7P6 = 7!/(7-6)! = 5040

Example 4: In how many ways can you make a committee of 3 students out of 10 students?

10C3 = 10!/(10-3)!3! = 120

--Danielle.