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: [142.225, 243.809, -41.935, 96.795, -99.067, 222.292, 113.486, 143.726]
Example Output: 102.666

Example Input: [112.141, 221.013, 75.929, -19.73, 151.257]
Example Output: 108.122

Example Input: [-20.618, 188.082, 108.928, 56.291, 121.601, 193.406, 81.14, -60.34, 162.33, -71.764]
Example Output:
75.906