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: [38.343, 177.478, 120.174, -74.923, 98.159]
Example Output: 71.846

Example Input: [146.815, 125.411, 84.472, -63.01, 79.256, -34.213, 248.004, -86.96, -39.397]
Example Output: 51.153

Example Input: [-72.023, 158.892, -59.403, -71.503, 124.717, -5.183, 76.91, 113.766]
Example Output:
33.272