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. Choose the most appropriate option:
A) 10sec B) 20sec C) 15sec D) 16sec E) 14sec
Explanation :   Time taken to cover the entire length = tot.dist/resultant speed = 150/ (12+3)= 
<gadget id="calculator">150/ (12+3)</gadget>
<output>10</output>
10sec   10secnswer : 10sec
<result>A</result>
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.