A walks at 10 kmph and 10 hours after his start, B cycles after him at 20 kmph. How far from the start does B catch up with A? Choose the correct choice from the following options:
A) 100km
B) 150km
C) 50km
D) 120km
E) 200km
Suppose after x km from the start B catches up with A. Then, the difference in the time taken by A to cover x km and that taken by B to cover x km is 10 hours.   x/10 - x/20 = 10   x = 200 km   Answer is 200km
<result>E</result>
A walks at 10 kmph and 10 hours after his start, B cycles after him at 20 kmph. How far from the start does B catch up with A?