To solve the problem, we need to determine the probability that an event, which happens with a probability of 0.4 per century, will occur at least once over 1,000 years. Here's the step-by-step solution:

1. Event Not Happening in a Century:

   • The probability of the event not happening in a single century is: $P(\text{not happening in a century}) = 1 - 0.4 = 0.6$

2. Event Not Happening in 1,000 Years:

   • There are 10 centuries in 1,000 years. If the event does not happen in each century, the overall probability of it not happening over 10 centuries is: $P(\text{not happening in 10 centuries}) = 0.6^{10}$ Now, we'll calculate $0.6^{10}$.

3. Event Happening at Least Once in 1,000 Years:

   • The probability that the event will happen at least once in 1,000 years is the complement of the probability that it never happens in 10 centuries: $P(\text{happening at least once}) = 1 - P(\text{not happening in 10 centuries}) = 1 - 0.6^{10}$ Let me calculate $0.6^{10}$.The probability of the event not happening over 1,000 years (10 centuries) is approximately $0.00605$.

4. Final Probability:

   • The probability that the event happens at least once in 1,000 years is: $P(\text{happening at least once}) = 1 - 0.00605 = 0.99395$ So, the probability of the event happening at least once in 1,000 years is approximately $0.99395$, or 99.4%.

Would you like more details or have any questions?

Here are 5 related questions:

1. What if the probability per century was 0.1? How would the result change?
2. How does the result change for different time periods, like 500 or 2,000 years?
3. What if the event happens twice in a century? How do we adjust the calculation?
4. How do you calculate the probability for more complex repeating events?
5. How can we model the probability of such events using a Poisson distribution?

Tip: Complementary probability (1 - P) is useful when calculating "at least one occurrence" scenarios!