To calculate yourself:
To calculate the probability of an event happening, you divide (number of times event can occur) by (total possible outcomes). For instance, the probability of rolling a 6 on a 6-sided die: there is 1 six (event), and 6 total sides (total outcomes), so the probability is 1/6.
To calculate the probability of multiple events happening (such as the multiple cards coming up with the same suit), then you take the probability (by method above) of each, and multiply them together. For instance, the probability of getting AA dealt to you:
P(first ace)
= 4(possible aces)/52(possible cards) and
P(second ace)
= 3(possible aces left)/51(possible cards left).
Then multiply them together, so you get:
P(first ace)
= 4/52
= 1/13
P(second ace)
= 3/51
= 1/17
P(getting dealt AA)
= 1/13*1/17
= 1/221 which is also equal to ~%0.5 or 220:1.
Sorry; feel like rambling a bit
:
so the probability of flopping a flush can be found this way:
P(1st spade)*P(2nd spade)*P(3rd spade)
= (11/50)*(10/49)*(9/48)
= 33/3920 = %0.84