a train 200 m long crosses a platform 200 m long in 40 sec ; find the speed of the train ?
"d = 200 + 200 = 400 t = 40 s = 400 / 40 * 18 / 5 = 36 kmph answer : e"
subtract(multiply(40, multiply(const_60.0, const_0_2778)), 200)