I've been looking at tables with the probabilities of flopping certain hands and I took to my calculator to try and see if I could figure them out myself.

I'm having trouble with the flopping quads with a starting pair. According to these tables, the probability of having a starting pair and flopping quads is 0.25% or 400 to 1. I don't seem to get this answer at all.

So if you already have a pair, then there are 2 outs with 50 remaining cards in the deck. So I did:

1-((48/50)x(48/49)x(47/48)) (assuming we hit an out on the first card of the flop, but I guess it doesn't really matter whether we get the 1st out on the first or second card, right?).

This gives me 7.9% or 11.8 to 1, which is way off what they have given.

So I'm assuming they factor in the probability of even getting dealt a pair to start with, which is 5.8% or 16.24 to 1 [(13C1)x(4C2) / 52C2].

How do you work it out?