Answer :
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
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