AT least One
If probability of event A happening is p and event B happening is q, then the probability that at least one of them happens is (p+q).
Example:
There are 20 quarters, 33 nickels, and 47 pennies in a jar. The probability that a randomly selected coin is a quarter= 20/(20+33+47)=20/100=0.2 and the coin is nickel = 33/100 =0.33.The probability it is either a quarter or a nickel = 0.2+0.33=0.53.
Remember:
The events needs to be mutually exclusive, that is if one happens the other cannot happen: a coin is either a quarter or nickel but not both.
