Answer & Explanation
C) 12 kmph
The distance is constant in this case.
Let the time taken for travel with a speed of 10 kmph be 't'.
Now the speed of 15 kmph is 3/2 times the speed of 10 kmph.
Therefore, time taken with the speed of 15 kmph will be 2t/3 (speed is inversely proportional to time)
Extra time taken = t - 2t/3 = t/3
=> 1pm - 11am = 2hrs
=> t/3 = 2h
=> t = 6 hrs.
Now, Distance = speed x time = 10 x 6 = 60 kms
Time he takes to reach at noon = 6 - 1 = 5 hrs
Now, Speed = 60/5 = 12 kmph.