If a man travels p hours at an average rate of q miles per hour, and then r hours at an average rate of s miles per hour, what is his overall average rate of speed?

Total miles traveled in p hours = p*q miles and 
Total miles traveled in r hours = r*s miles
so, average rate of speed = total miles traveled / number of hours
                                     =[{(p*q)+(r*s)} / (p+r)] miles per hour

The answer would be -3.9> -4.5