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: [229.461, -89.251, 170.954]
Example Output: 103.721

Example Input: [-29.727, 150.587, -28.344, 181.096, 0.275, -91.658, 169.609, -21.106, 153.48]
Example Output: 53.801

Example Input: [-31.921, -39.036, 212.583, -44.259, 27.385, 95.851, 27.055, 153.172]
Example Output:
50.104