a train speeds past a pole in 15 seconds and a platfrom 100 m long in 25 seconds . its length is :
"sol . let the length of the train be x metres and its speed be y m / sec . they , x / y = 15 ⇒ y = x / 15 ∴ x + 100 / 25 = x / 15 ⇔ x = 150 m . answer d"
multiply(100, subtract(const_2, const_1))