a train covers a distance of 18 km in 10 min . if it takes 9 sec to pass a telegraph post , then the length of the train is ?
"speed = ( 18 / 10 * 60 ) km / hr = ( 108 * 5 / 18 ) m / sec = 30 m / sec . length of the train = 30 * 9 = 270 m . answer : c"
divide(18, subtract(divide(18, 10), 9))