A boat crossed a lake from West to South at the speed of 8 km/h, entered a river and covered twice as much distance going upstream at 7 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?  Pick.
A) 4 B) 5 C) 6 D) 7 E) 9
One way of solving this is:   Speed of boat on still water (lake)=8kmph   Speed upstream = 7kmph = speed in still water - speed of river =&gt; speed of river = 1kmph   =&gt;Speed downstream = speed in still water + speed of river = 8+1= 
<gadget id="calculator">8+1</gadget>
<output>9</output>
9kmph   Ans is 9
<result>E</result>
A boat crossed a lake from West to South at the speed of 8 km/h, entered a river and covered twice as much distance going upstream at 7 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?