In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.

Example Input: [15.293, 221.056, 241.387, 81.3, 102.644, 146.885, -33.65, -36.56, -69.176]
Example Output: 74.353

Example Input: [185.805, 8.01, 151.056, 35.572, 51.884, 217.1, -0.547, 8.171]
Example Output: 82.131

Example Input: [145.697, -40.957, -46.926, -55.065, 177.211, 204.811, -94.192, -47.466]
Example Output:
30.389