Problem: in one hour , a boat goes 8 km along the stream and 2 km against the stream . the sped of the boat in still water ( in km / hr ) is :
Rationale: "solution speed in still water = 1 / 2 ( 8 + 2 ) km / hr = 5 kmph . answer b"
annotated_formula: divide(add(8, 2), const_2)