A boat can travel with aspeed of 30km/hr in still water. If the speed of the stream is 5km/hr, find the time taken by the boat to go 70km downstream. Options:  A) 1 hr  B) 2 hrs  C) 3 hrs  D) 4 hrs  E) 5 hrs

Rationale: "speed downstream = ( 30 + 5 ) km / hr = 35 km / hr . time taken to travel 68 km downstream = 70 / 35 hrs = 2 hrs . b"
Answer: B