PSA_PRACTICE_QNR34. It takes an escalator 20 seconds to move a person from the first floor to the second.If not operating, Jose takes 30 seconds to walk up on the still escalator. If Jose walks while the escalator is moving, how long does it take for him to reach the second floor?
Ans: Let the distance from first floor to the second one be ‘d’.
Escalator takes 20 seconds to cover ‘d’; speed of escalator= d/20
Jose alone takes 30 seconds to cover ‘d’; speed of escalator= d/30
When Jose is walking while the escalator is also moving, speed is added.
Relative speed = d/20 + d/30
The time he takes now to reach second floor = distance/relative speed = d / (d/20 + d/30) = 12 seconds.