What does the number of drinks with coffee and the number of drinks with dairy sum to?
P(both coffee and dairy)=0
P(neither coffee nor dairy)=0
Practice makes perfect
From the exercise we know that there are a total of 63 drinks at the coffee shop. Of these drinks, 42 contain coffee and 21 contain dairy. Since the sum of these drinks equals 63, there can be no drinks that contain both coffee and dairy. It must also mean that there is no chance of getting a drink that does not contain coffee nor dairy.
P(Both coffee and dairy)&=0
P(Neither coffee nor dairy)&=0
Let's illustrate this as a two-way table.
