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: [65.486, -51.995, 170.628, -23.998, 83.128, -57.38, 130.737, 214.738]
Example Output: 66.418

Example Input: [103.885, 191.867, 82.228, 177.708, 136.093, -17.022]
Example Output: 112.46

Example Input: [74.43, 138.738, 114.237, 138.845, 188.957, 103.103, -43.988, -68.085, 157.274]
Example Output:
89.279