Problem: in one hour , a boat goes 11 km along the stream and 5 km against the stream . the speed of the boat in still water ( in km / hr ) is :
Rationale: "solution speed in still water = 1 / 2 ( 11 + 5 ) kmph . = 8 kmph . answer c"
annotated_formula: divide(add(11, 5), const_2)