probability question

[staticRhymes]

I'm reading Harrington's book Vol 1, and he's got a situation where you are dealt AdAc
flop comes 9h5c2s.

It's between you and another person and he goes all in.

It says that if he's got 99's or 55's then you have a 10% chance in winning. If he holds KK's, QQ's, JJ's or TT's you've got a 92% chance in winning.

However he didn't not give reasoning for the 10% or 92% probability. Can someone here kindly do so?

As well, in another situation, you're dealth QdQs, flop comes Ah9c3s and he says that if the someone's holding and A, you're a 9-1 underdog, which I understand to be 10% chance of winning.

So if you're in a situation where you need turn a pair into a set, is there a 10% chance of doing it and you just have to remember or do you do this sort of math in certain situaitons on the fly?

thanks in advance for the help.

[aaronw]

It is just simple mathematics. See the poker calculator on this site for confirmation if you would like.

As for doing these on the fly, you just start to remember them after seeing them so many times. If it is one you don't know, a simple formula is to take the amount of outs you have and multiply it by (the number of streets left * 2) IE- 2 outs on the flop for the turn is ~ 4%. for the turn AND river its ~8%. These numbers are probably off a little bit but generally give you a general idea of where you are at.