an escalator moves towards the top level at the rate of 7 ft . sec and its length is 180 feet . if a person walks on the moving escalator at the rate of 2 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 = 180 / ( 7 + 2 ) = 20 sec answer : c"
divide(180, add(7, 2))