Which is the same thing as n k n-k. For an in-depth explanation of the formulas please visit Combinations and Permutations. 4 6 displaystyle _ nC_ r frac 10 4 6.
The number of ways of arranging n unlike objects in a line is n.
In another example - if you want to estimate how many computing hours you need to brute force a hashed password you calculate the number of permutations not the number of combinations. For an in-depth explanation of the formulas please visit Combinations and Permutations. Looking at the formula we must calculate 6 choose 2. In another example - if you want to estimate how many computing hours you need to brute force a hashed password you calculate the number of permutations not the number of combinations.