Problem: a man swims downstream 100 km and upstream 30 km taking 10 hours each time ; what is the speed of the current ?
Rationale: "100 - - - 10 ds = 10 ? - - - - 1 30 - - - - 10 us = 3 ? - - - - 1 s = ? s = ( 10 - 3 ) / 2 = 3.5 answer : b"
annotated_formula: divide(add(divide(30, 10), divide(100, 10)), const_2)