A walks at 10 kmph and 5 hours after his start, B cycles after him at 20 kmph. How far from the start does B catch up with A?
Pick:
A) 100 km	B) 150 km	C) 50 km	D) 120 km	E) 200 km

Rationale: "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 5 hours . x / 10 - x / 20 = 5 x = 100 km answer is a"
Answer: A