Correct Answer: (d) 25 km
Solution:Prerna travels only for 3 hour, since half an hour she halts at Place B.
Let the time for which she travels at 50 km/h be x hours, therefore she travels at 30 km/h for (3 – x) hours.
Now A to C,
50x + 30(3 – x) = 100
Solving, we get x = ½
So, Prerna travels for half an hour @ 50 km/h from Place A to B. Therefore, distance between A and B = ½ × 50 = 25 kms.