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: [38.24, 196.576, -84.173, -45.001, 1.607, 170.177, 234.811, -60.183, -91.513]
Example Output: 40.06

Example Input: [242.148, 97.472, -15.031, 246.784, 54.233, -27.114]
Example Output: 99.749

Example Input: [243.624, 129.219, -7.592]
Example Output:
121.75