#### Question:

Automobiles traveling on a road with a posted speed limit of 55 miles per hour are checked for speed by a state police radar system. Following is a frequency distribution of speeds.

Speed (miles per hour) 45-49 50-54 55-59 60-64 65-69 70-74 75-79

Frequency 10 40 150 175 75 15 10

Total 475a.What is the mean speed of the automobiles traveling on this road? b.Compute the variance and the standard deviation.