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: [246.282, 231.815, 1.709, -51.234, -76.432, 21.802, 18.917, 106.734, 168.909, -67.647]
Example Output: 60.085

Example Input: [121.069, 12.661, 159.825, -39.645, 6.609, 156.735, 110.054, 112.875]
Example Output: 80.023

Example Input: [-28.295, -24.828, -66.96, -12.108, -96.597, 110.99, 172.86, -18.752, 157.717]
Example Output:
21.559