An airline gathers data on late departures and early arrivals over a month. It finds that the probability of a late departure is 12 percent, the probability of an early arrival is 27 percent, and the probability of both a late departure and an early arrival is 4 percent.

Which equation shows how to correctly calculate the probability of a late departure or an early arrival?

A. [tex]P(\text{late departure or early arrival}) = 0.12 + 0.04[/tex]

B. [tex]P(\text{late departure or early arrival}) = 0.12 + 0.27[/tex]

C. [tex]P(\text{late departure or early arrival}) = 0.12 + 0.27 - 0.04[/tex]

D. [tex]P(\text{late departure or early arrival}) = 0.27 + 0.04 - 0.12[/tex]



Answer :

To find the probability of either a late departure or an early arrival, we must consider the probabilities of both events, as well as the intersection where both events happen simultaneously.

We are given:
- The probability of a late departure ([tex]\(P(\text{Late Departure})\)[/tex]) is 12 percent, or 0.12.
- The probability of an early arrival ([tex]\(P(\text{Early Arrival})\)[/tex]) is 27 percent, or 0.27.
- The probability of both a late departure and an early arrival ([tex]\(P(\text{Late Departure} \cap \text{Early Arrival})\)[/tex]) is 4 percent, or 0.04.

The correct formula to calculate the probability of either a late departure or an early arrival involves the principle of inclusion and exclusion:
[tex]\[ P(\text{Late Departure} \cup \text{Early Arrival}) = P(\text{Late Departure}) + P(\text{Early Arrival}) - P(\text{Late Departure} \cap \text{Early Arrival}) \][/tex]

Putting the given probabilities into this equation:
[tex]\[ P(\text{Late Departure} \cup \text{Early Arrival}) = 0.12 + 0.27 - 0.04 \][/tex]

Carrying out the arithmetic:
[tex]\[ P(\text{Late Departure} \cup \text{Early Arrival}) = 0.35000000000000003 \][/tex]

Therefore, the correct choice, which shows how to accurately calculate the probability of a late departure or an early arrival, is:
[tex]\[ P(\text{Late Departure or Early Arrival}) = 0.12 + 0.27 - 0.04 \][/tex]

This corresponds to the third option from the given list.