Problem: a 600 meter long train crosses a signal post in 40 seconds . how long will it take to cross a 3 kilometer long bridge , at the same speed ?
Rationale: "s = 600 / 40 = 15 mps s = 3600 / 15 = 240 sec = 4 min . answer : a"
annotated_formula: divide(divide(multiply(3, const_1000), speed(600, 40)), const_60)