the length of the bridge , which a train 250 metres long and travelling at 72 km / hr can cross in 30 seconds , is :
"speed = [ 72 x 5 / 18 ] m / sec = 20 m / sec time = 30 sec let the length of bridge be x metres . then , ( 250 + x ) / 30 = 20 = > 250 + x = 600 = > x = 350 m . answer : d"
subtract(multiply(divide(multiply(72, speed(const_1000, const_1)), speed(const_3600, const_1)), 30), 250)