Let d = distance (in km)
Let t = the correct time to reach (in hours)
When traveling at 3 kmph, Ananyaa is 15 minutes late.
Time taken = 3d hours
15 minutes = 6015=41 hour
3d=t+41 ... (Equation 1)
When traveling at 4 kmph, Ananyaa is 15 minutes early.
Time taken = 4d hours
4d=t−41 ... (Equation 2)
Subtracting Equation 2 from Equation 1:
3d−4d=(t+41)−(t−41)
3d−4d=t+41−t+41
3d−4d=21
124d−123d=21
12d=21
d=6
Therefore, the distance is 6 km.