In some cases, a deck of playing cards consists of 52 cards and 6 cards randomly selected to form a flush.

There are 52 cards in a deck of playing cards. There are several ways to form a flush, which can be obtained by calculating the probability.

First, we need to define a straight flush. In poker, a straight flush consists of five consecutive cards of the same suit. Each suit has 13 cards (A, 2, 3, 4, 5, 6, 7, 8, 9, 10, J, Q, K), so the possibility of forming a flush is as follows:

1.5 connection: there are 10 combinations (such as a, 2, 3, 4, 5).

2. Five continuous straights including A and K: There are two combinations (A, 2, 3, 4, 5 and 10, J, Q, K and A).

So there are 12 kinds of straight flushes.

Next, we need to calculate the number of combinations of 6 cards selected from 52 cards. According to the calculation formula of combination number, that is, c (52,6) = 52! / (6! * (52-6)! ), we can get that the combination number of 6 cards selected from 52 cards is 20,358,520.

Finally, the ratio of the number of cases constituting the flush to the total number of combinations can be calculated, that is,12/20,358,520 ≈ 0.000589.

Therefore, it is about 0.0000589% that 6 cards are randomly selected from 52 cards to form a straight flush. This is a fairly small probability.