If a man walks at 6 kmph, he can reach his destination at 9:00 am. However, he walks a little slower and reaches only at 10:00 am. If the distance to his destination was 12 km, at what speed did he walk?

A. 5 kmph
B. 4 kmph
C. 4.5 kmph
D. 3 kmph

If he travels at 6 kmph,
time taken to reach = 12/6 = 2 hours But he takes 3 hours.
Speed = 12/3 = 4 kmph