A boat can travel with a speed of 25km/hr in still water. If the speed of the stream is 5km/hr, find the time taken by the boat to go 90km downstream.  Pick.
A) 1 hr	B) 2 hrs	C) 3 hrs	D) 4 hrs	E) 5 hrs

Rationale: "speed downstream = ( 25 + 5 ) km / hr = 30 km / hr . time taken to travel 90 km downstream = 90 / 30 hrs = 3 hrs . answer : c"
Answer: C