A person can row at 10 kmph in still water. If the velocity of the current is 2 kmph and it takes him 15 hour to row to a place and come back, how far is the place?
Select:  A) 24 km  B) 30 km  C) 48 km  D) 72 km  E) 15 km

Rationale: "speed of down stream = 10 + 2 = 12 kmph speed of upstream = 10 - 2 = 8 kmph let the required distance be xkm x / 12 + x / 8 = 15 2 x + 3 x = 360 x = 72 km answer is d"
Answer: D