A boat sails 15 km of a river towards upstream in 5 hours. How long will it take to cover the same distance downstream, if the speed of current is one-fourth the speed of the boat in still water:	Choose the most appropriate option
A) 1.8h  B) 3h  C) 4h  D) 5h  E) None of these
Explanation:   Upstream speed = 3h-S   Downstream speed = 3h + s   3h - S = 15/5= 
<gadget id="calculator">15/5</gadget>
<output>3</output>
3 km/h   Again 3h= 4S   Therefore 3h - S = 3 = 3S   =&gt; S = 1 and 3h = 4 km/h   Therefore 3h + S = 5km/h   Therefore, Time during downstream = 15/5= 
<gadget id="calculator">15/5</gadget>
<output>3</output>
3h   Answer: 3h
<result>B</result>
A boat sails 15 km of a river towards upstream in 5 hours. How long will it take to cover the same distance downstream, if the speed of current is one-fourth the speed of the boat in still water: