Problem: a 750 m long train crosses a platform in 39 sec while it crosses a signal pole in 18 sec . what is the length of the platform ?
Rationale: "speed = 750 / 18 = 125 / 3 m / sec . let the length of the platform be x meters . then , ( x + 750 ) / 39 = 125 / 3 = > x = 1625 m . l = 1625 - 750 = 875 answer : option b"
annotated_formula: subtract(multiply(speed(750, 18), 39), 750)