Final answer:
The probability of either event A or event B occurring is calculated using the formula P(A OR B) = P(A) + P(B) - P(A AND B). Given P(A) = 1/5, P(B) = 2/5, and P(A AND B) = 1/5, the result is P(A OR B) = 2/5.
Step-by-step explanation:
To find the probability of either event A or event B occurring (denoted as P(A OR B)), we use the formula for the union of two events, which factors in the probability of each individual event and subtracts the probability of both events happening together. The formula is P(A OR B) = P(A) + P(B) - P(A AND B). Using the given probabilities: P(A) = 1/5, P(B) = 2/5, and P(A AND B) = 1/5, we substitute these values into the formula to calculate the unknown probability.
Using the formula, we have:
P(A OR B) = (1/5) + (2/5) - (1/5) = 2/5.
Therefore, the probability of event A or event B occurring is 2/5.