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: [39.88, 58.489, 225.343, 105.008, 210.581, 35.577]
Example Output: 112.48

Example Input: [-30.66, 134.777, 39.637, -41.053, 60.502, -99.875, -32.055, 51.52, 216.645, 11.994]
Example Output: 31.143

Example Input: [68.753, 227.258, -67.293, 20.852, -48.419, 244.182, 75.629, 146.521, 23.542]
Example Output:
76.781