Question

Are the number of permutations of two items from a data set always twice the number of combinations when taking two items from the same set?

Answer 1

Yes. The number of permutations is two. The number of combinations is one.

Answer 2

Yes.
nPr = \[n! \over (n - 2)!\]
nCr = \[n! \over (n - 2)! 2!\]
When you simplify things, it will always be divided by 2 since 2! = 2 * 1 = 2.

Answer 3

Awsome. I've been struggling with this one.