calculate probabilty OF and ODDS

[hcc221]

How do you calculate the probability OF and ODDS of picking a black card or an ace cards?

i think the formula for it is P(e)/ P(e')
there's 26 black cards
and 4 ace cards.

the part of the question with "or" got me confused

 

[galactus]

The probability of a black card OR an Ace are not mutually exclusive.

We have to subtract the black Aces. otherwise, we double count.

\(\displaystyle \frac{26}{52}+\frac{4}{52}-\frac{2}{52}=\frac{28}{52}=\frac{7}{13}\)

Odd is the ratio of for and against.

\(\displaystyle 28:24=7:6\) is the odds. 28+24=52. 28 FOR and 24 AGAINST