Poker maths and understanding probability is important to help our decision making process. It must be stressed that you do not need to be a maths wizard to play poker. Knowing the rough odds is more than enough to allow us to come to sound conclusions. The trick in Poker is being able to tell the difference between a good wager to make/accept and a bad one.
We need to remember the '4 Times and 2 Times' rule when working out the rough probability of hitting our drawing hand. First we need to calculate our 'outs', we then take this number and if we are on the flop multiply it by 4 to give us the rough percentage chance of hitting our hand by the river.
For example; if we hold 910 and have a flush draw on a 3k2 flop, any of the following 9 cards in the deck will give us a flush:
We therefore have 9 outs to make our flush. We then multiply 9 by 4 to give us 36, this is the rough percentage chance that we will hit our hand by the river. On the turn (with one card to come) we count our 'outs' again and multiply by 2 to give us the rough percentage chance of hitting.
This equation for calculating the chances of hitting outs can be expressed more clearly as:
Number of outs X 4 (if we are on the flop)= our rough percentage chance of hitting by the river.
Number of outs X 2 (if we are on the turn)= our rough percentage chance of hitting by the river.