Problem: in one hour , a boat goes 19 km along the stream and 5 km against the stream . the speed of the boat in still water ( in km / hr ) is :
Rationale: "sol . speed in still water = 1 / 2 ( 19 + 5 ) kmph = 12 kmph . answer d"
annotated_formula: divide(add(19, 5), const_2)