Aiden surveyed the students on his bus to find out how many minutes they spent on their homework last night.

The deviations from the mean can be found by subtracting the mean from each data point:

10 - 20 = -10
5 - 20 = -15
15 - 20 = -5
20 - 20 = 0
40 - 20 = 20
30 - 20 = 10

The sum of the deviations is -10 + (-15) + (-5) + 0 + 20 + 10 = -10 - 15 - 5 + 20 + 10 = 30.

Therefore, the sum of the deviations is 30.