In a river flowing at 2 km/hr, a boat travels 40 km upstream and then returns downstream to the starting point. If its speed in still water be 6 km/hr, find the total journey time.
Choose the correct choice from the following.
A) 10 hours	B) 12 hours	C) 14 hours	D) 15 hours	E) None of these
Explanation :   speed of the boat = 6 km/hr   Speed downstream = (6+2)= 
<gadget id="calculator">(6+2)</gadget>
<output>8</output>
8 km/hr   Speed upstream= (6-2)= 
<gadget id="calculator">(6-2)</gadget>
<output>4</output>
4 km/hr   15 hoursistance travelled downstream= 15 hoursistance travelled upstream = 40 km   Total time taken = Time taken downstream + Time taken upstream   = (40/8) + (40/4)= 
<gadget id="calculator">(40/8) + (40/4)</gadget>
<output>15</output>
15   15 hours
<result>D</result>
In a river flowing at 2 km/hr, a boat travels 40 km upstream and then returns downstream to the starting point. If its speed in still water be 6 km/hr, find the total journey time.