An escalator moves towards the top level at the rate of 15 ft.sec and its length is 180 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 correct answer
A) 12sec	B) 20sec	C) 15sec	D) 18sec	E) 10sec
10secxplanation :   Time taken to cover the entire length = tot.dist/resultant speed = 180/ (15+3)= 
<gadget id="calculator">180/ (15+3)</gadget>
<output>10</output>
10sec   Answer : 10sec
<result>E</result>
An escalator moves towards the top level at the rate of 15 ft.sec and its length is 180 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.