an escalator moves towards the top level at the rate of 12 ft . sec and its length is 210 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 .
"time taken to cover the entire length = tot . dist / resultant speed = 210 / ( 12 + 2 ) = 15 sec answer : a"
divide(210, add(12, 2))