Question

historically on given day at CHS there is a 9% chance of a fire drill and 6% chance of a tornado drill if there is a 2% chance, we will have both a fire drill and a tornado drill on a given day the what would be the probability that a day in late September would have either a fire drill or a tornado drill? round to the nearest thousandths

Answer 1

To find the probability of having either a fire drill or a tornado drill, we can use the principle of inclusion-exclusion. The probability of either event occurring is calculated as follows:

\[ P(A \cup B) = P(A) + P(B) - P(A \cap B) \]

Where:
- \( P(A) \) is the probability of having a fire drill.
- \( P(B) \) is the probability of having a tornado drill.
- \( P(A \cap B) \) is the probability of having both a fire drill and a tornado drill.

From the problem, we have:
- \( P(A) = 0.09 \) (9% chance of a fire drill)
- \( P(B) = 0.06 \) (6% chance of a tornado drill)
- \( P(A \cap B) = 0.02 \) (2% chance of both drills)

Now we can substitute these values into the formula:

\[
P(A \cup B) = P(A) + P(B) - P(A \cap B)
\]
\[
P(A \cup B) = 0.09 + 0.06 - 0.02
\]
\[
P(A \cup B) = 0.13
\]

Therefore, the probability of having either a fire drill or a tornado drill is 0.13, or 13%.

Rounding to the nearest thousandths, the final answer is:

**0.130**