a train covers a distance of 12 km in 10 minutes . if it takes 6 seconds to pass a telegraph post , then the length of the train is :
"sol . speed = [ 12 / 10 * 60 ] km / hr = [ 72 * 5 / 18 ] m / sec = 20 m / sec . length of the train = ( speed * time ) = ( 20 * 6 ) m = 120 m . answer a"
divide(const_100.0, subtract(divide(const_100.0, 10), 6))