Finding probability value using normal approximation for the given values.
The rain following in Columbus County in a year is 50 inches with a standard deviation of 9 inches. What is the probability of a randomly selected year Columbus County will receive the following amounts of rainfall. (Suppose variable is normally distributed).
1. At least 54 inches
2. At least 63 inches
3. between 45 and 55 inches
4. How many inches of rain would be considered an extremely (only happens once in a 100 years) dry year?