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: [13.21, 76.551, 51.016, 230.763, 149.792, 157.216, 117.414, 144.272, 5.805, 118.165]
Example Output: 106.42

Example Input: [213.2, 159.287, 214.859, 189.464, 185.706, -85.847, 215.647, 8.545]
Example Output: 137.608

Example Input: [30.99, 197.577, 211.905, 130.898, 10.106, -15.097, 139.3, 71.536, 114.755]
Example Output:
99.108