A boat running downstream covers a distance of 20 km in 2 hours while for covering the same distance upstream,it takes 5 hours.What is the speed of the boat in still water ?
Options:	A) 4 km/hr	B) 6 km/hr	C) 7 km/hr	D) Data inadequate	E) None of these
Solution   Rate downstream =(20/2)= 
<gadget id="calculator">(20/2)</gadget>
<output>10</output>
10 kmph, Rate upstream=(20/5)= 
<gadget id="calculator">(20/5)</gadget>
<output>4</output>
4 kmph.   ∴ Speed in still water=1/2(10+4) kmph = 7 kmph. Answer 7 km/hr
<result>C</result>
A boat running downstream covers a distance of 20 km in 2 hours while for covering the same distance upstream,it takes 5 hours.What is the speed of the boat in still water ?