A boat can travel with a speed of 15 km/hr in still water. If the speed of the stream is 6 km/hr, find the time taken by the boat to go 86 km downstream.	Choose the correct answer.
A) 4.1 hr	B) 5.25 hr	C) 8.25 hr	D) 2.25 hr	E) 2.50 hr

Rationale: "speed of boat in still water = 15 km / hr speed of the stream = 6 km / hr speed downstream = ( 15 + 6 ) = 21 km / hr time taken to travel 86 km downstream = 86 â  „ 16 = 17 â  „ 4 = 4.1 hours answer is a"
Answer: A