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. Choose the most appropriate option: A) 5sec B) 25sec C) 20sec D) 15sec E) 10sec
Explanation :   Time taken to cover the entire length = tot.dist/resultant speed = 180/ (7+2)= 
<gadget id="calculator">180/ (7+2)</gadget>
<output>20</output>
20sec   Answer : 20sec
<result>C</result>
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.