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: [15.491, 60.283, 240.958, 155.995, 35.585, -55.875, 82.379, 142.503, 95.176, 85.281]
Example Output: 85.778

Example Input: [87.258, 29.558, -48.199, -28.615, 46.642]
Example Output: 17.329

Example Input: [245.134, 62.209, 94.18, 238.218, 28.385, 150.906, 139.02, 246.925, 126.08]
Example Output:
147.895