Pre-Flop Winning Probabilities

[PJM1206]

I was hoping someone could show me the calculation or source of how pre-flop winning probabilites are calculated. In Harrington's book he asserts the following probabilities:
1. High pair vs low pair 4.5 to 1
2. pair vs two higher cards 55 to 45
3. pair vs two lower cards 5 to 1
4 pair vs a higher and a lower card 5 to 2
5. two higher cards vs two lower cards 5 to 3

any one know the basis of these numbers?

[KJL]

I think this thread answers that. link

[PJM1206]

thanks