The speed of a boat in still water is 36 kmph. What is the speed of the stream if the boat can cover 80 km downstream or 40 km upstream in the same time? Choose the most appropriate option:
A) 10 kmph B) 14 kmph C) 12 kmph D) 16 kmph E) 15 kmph
X = the speed of the stream   (36 + X) / (36 - X) = 2/1   36+ X = 72 - 2X   3X = 36   X = 12 km/hour   If the speed of the stream is 12km/hour, then the 'downstream' speed of the boat is   36+12= 
<gadget id="calculator">  36+12</gadget>
<output>48</output>
48km/hour and the 'upstream' speed of the boat is 36-12= 
<gadget id="calculator">36-12</gadget>
<output>24</output>
24km/hour. In that way, if the boat traveled for 2 hours, it would travel 2x48= 96km downstream and 2x24 = 48 km/hour upstream.   Answer : 12 kmph
<result>C</result>
The speed of a boat in still water is 36 kmph. What is the speed of the stream if the boat can cover 80 km downstream or 40 km upstream in the same time?