A boat crossed a lake from North to East at the speed of 7 km/h, entered a river and covered twice as much distance going upstream at 6 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 one:
A) 4  B) 5  C) 6  D) 7  E) 8

Rationale: "one way of solving this is : speed of boat on still water ( lake ) = 7 kmph speed upstream = 6 kmph = speed in still water - speed of river = > speed of river = 1 kmph = > speed downstream = speed in still water + speed of river = 7 + 1 = 8 kmph ans is e"
Answer: E