Probability & Statistics (38 of 62) Permutations and Combinations - Example 3

In this video I will find the permutation and combination of 5 colors in 5,4,3,2,1 spaces.

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[zhoudai]

Don't look at the formula, look at the process of solving problem, the importance is on the thought not the formula!

Permutation is just combination with order, consider taking 5 units from 5 units, for combination you only have 1 choice, while for permutation those 5 units can be re-arranged with different orders, so multiply with 5!, easy as it.

Same in other cases, multiply the result of combination with n!, you get permutation! (Be careful about what n is though, it may change.)

[John-lfxf]

Why not use the permutations formula similar in form to the combinations formula. The nPk=n!/(n-k)!
This is what we are using in our PreCalculus class

[gooddeedsleadto]

Should we look at it as if combinations are the number of columns
and permutations are a number of records for each column? Thanks

[majedmalhies]

professor,
for permutations you can use the same formula that you use for combinations, but without a k! in the denominator

[Hany_AlShahhat]

why nPn equals nP(n-1) ??(5P5, 5P4)
i know i can derive this from the permutation equation, because 0! and 1! are equal to 1, so i get the same result , but still it's not something intuitive and i'm confused, could you please elaborate it !

[mekhailvarnamkhasti]

You made a mistake on the 5 combination and 2 spaces. The answer is 20, not 10.