a train speeds past a pole in 15 seconds and a platform 100 m long in 40 seconds . its length is ?
"let the length of the train be x meters and its speed be y m / sec . they , x / y = 15 = > y = x / 15 x + 100 / 40 = x / 15 x = 100 m . answer : d"
multiply(100, subtract(const_2, const_1))