A person preparing for Olympics Games ran 9 km in 1 hour and 20 minutes, and then 12 km in 1 hour and 40 minutes. What is the average speed in km/hr?

(A) 4 km/hr
(B) 5 km/hr
(C) 6 km/hr
(D) 7 km/hr

The answer is: (D) 7 km/hr
Solution
Total Distance = 9km + 12km = 21 km. And, Total Time = 1 hour 20 + 1 hour 40 = 3 hours. Hence, Average Speed is