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: [209.13, -12.632, 247.489, 55.492, 8.967, -90.158, 193.743]
Example Output: 87.433

Example Input: [128.472, 149.361, 71.023, -96.651]
Example Output: 63.051

Example Input: [-83.324, 218.716, 30.175, 118.622, -27.614, -95.184, 64.175, 191.032, -42.857, 92.122]
Example Output:
46.586