A boat crossed a lake from North to East at the speed of 10 km/h, entered a river and covered twice as much distance going upstream at 9 km/h. It then turned around and stopped at the south shore of the lake. If it averaged 3.8 km/h that day, what was its approximate downstream speed?	Choose the correct option.
A) 4	B) 5	C) 6	D) 7	E) 11
One way of solving this is:   Speed of boat on still water (lake)=10kmph   Speed upstream = 9kmph = speed in still water - speed of river =&gt; speed of river = 1kmph   =&gt;Speed downstream = speed in still water + speed of river = 10+1= 
<gadget id="calculator">10+1</gadget>
<output>11</output>
11kmph   Ans is 11
<result>E</result>
A boat crossed a lake from North to East at the speed of 10 km/h, entered a river and covered twice as much distance going upstream at 9 km/h. It then turned around and stopped at the south shore of the lake. If it averaged 3.8 km/h that day, what was its approximate downstream speed?