Problem: a train speeds past a pole in 15 seconds and a platform 120 meters long in 25 seconds . what is the length of the train ( in meters ) ?
Rationale: "let the length of the train be x meters . the speed of the train is x / 15 . then , x + 120 = 25 * ( x / 15 ) 10 x = 1800 x = 180 meters the answer is d ."
annotated_formula: multiply(120, subtract(const_2, const_1))