The temperature was in the range of 10-13 on 7 of the days.
Give it the weight of the middle of the range = 11.5 for 7 times = 80.5
The temperature was in the range of 14-17 on 9 of the days.
Give it the weight of the middle of the range = 15.5 for 9 times = 139.5
The temperature was in the range of 18-21 on 16 of the days.
Give it the weight of the middle of the range = 19.5 for 16 times = 312
The temperature was in the range of 22-25 on 22 of the days.
Give it the weight of the middle of the range = 23.5 for 22 times = 517
The temperature was in the range of 26-29 on 6 of the days.
Give it the weight of the middle of the range = 27.5 for 6 times = 165
Total weight for all ranges = (80.5 + 139.5 + 312 + 517 + 165) = 1,214
Total number of days = 60
Estimated mean temperature = (1,214) / (60) = 20.23°C
