City A to city B, Raja drove for 1 hour at 72 mph and for 3 hours at 80 mph. What was the average speed for the whole trip?
Select the correct option:
A) 57  B) 57.5  C) 78  D) 59  E) 62
The total distance is 1×72+3×80=312   And the total time is 4 hours. Hence,   Average Speed=(Total Distance/Total Time)=312/4= 
<gadget id="calculator">312/4</gadget>
<output>78</output>
78   Answer : 78
<result>C</result>
City A to city B, Raja drove for 1 hour at 72 mph and for 3 hours at 80 mph. What was the average speed for the whole trip?