You travel by Delhi Metro everyday from Botanical Garden, Noida to Hauz Khas, Delhi. At Hauz Khas metro station, you use an escalator to get out from the station. The escalator takes 80 seconds. One day, escalator was not working and you walk up the escalator in 50 seconds. How many minutes does it approximately take you to walk down the working escalator?
Explanation:
Let, the number of steps on the escalator be LCM(80, 50) = 400
∴ Speed of escalator = 400/80 = 5 steps/ second, and
Speed of the person = 400/50 = 8 steps/ second
When the person tries to go up a moving down escalator, the effective speed of the person = (8 − 5) steps /second = 3 steps/second
∴ Time taken = 400/3 = 133.33 steps/ second = 2.2 minutes (approx.)
Hence, option (b).
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