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: [21.953, -90.519, 92.624, 189.808, 130.57, -33.423, -16.126, 31.61, 119.582]
Example Output: 49.564

Example Input: [113.238, 247.072, -31.448, -33.563, 74.519, 67.841]
Example Output: 72.943

Example Input: [207.117, 121.279, 23.27, 231.597, -49.636, 28.83, 84.584, -87.796, 19.494]
Example Output:
64.304

