an escalator moves towards the top level at the rate of 12 ft . sec and its length is 150 feet . if a person walks on the moving escalator at the rate of 3 feet per second towards the top level , how much time does he take to cover the entire length .
"explanation : time taken to cover the entire length = tot . dist / resultant speed = 150 / ( 12 + 3 ) = 10 sec answer : a"
divide(150, add(12, 3))