Problem: a man whose speed is 5 kmph in still water rows to a certain upstream point and back to the starting point in a river which flows at 1.5 kmph , find his average speed for the total journey ?
Rationale: "m = 5.0 s = 1.5 ds = 6.5 us = 3.5 as = ( 2 * 6 * 3 ) / 10 = 4.55 answer : e"
annotated_formula: divide(add(5, subtract(5, 1.5)), const_2)