Say you have the usual 52$52$ card deck, 13$13$ ranks and 4$4$ suits. If I have a hand of 6$6$ cards, how many hands are there where at least half the cards have an odd number as rank? they can be of any suit.
This is what I'm doing: So 13
So $13$ ranks (assume they're numbered from 1$1$ to 13$13$ and the ace is a one) , this means that there are 7$7$ odd ranks (1$1$, 3$3$, 5$5$, 7$7$, 9$9$, 11$11$, 13$13$). We want half meaning at least 3$3$ of the 6$6$ cards in my hand need to be odd. So:
I want the cases where there 3$3$ odd cards + 4$+ 4$ odd cards + 5$+ 5$ odd cards + 6$+ 6$ odd cards. Is this how to represent it? $7\choose3 $ + $7\choose4 $ + $7\choose5 $ + $7\choose6 $ I
$$\frac 73 + \frac74 + \frac 75 +\frac76 $$
I feel like I'm missing something