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Thu 3 Aug, 2006 08:38 am
I'm not good at these sorts of questions but would appreciate it if someone could point me in the right direction as to how to do it: A boy takes 90 seconds to walk up a 'down' escalator. When not working he takes 30 seconds to walk down it at the same pace. How long would it take him to walk down it (again at the same pace) if it was working normally?
Let D = the distance, v = the man's speed, and E = the escalator's speed.
D/v = 30
D/(v - E) = 90
We seek D/(v + E).
v/D = 1/30
(v - E)/D = 1/90
2(v/D) - (v-E)/D = (2v - v + E)/D = (v + E)/D = 2(1/30) - 1/90 = 6/90 - 1/90 = 5/90
D/(v + E) = 90/5 = 18 (seconds)
Thank you very much indeed
Thanks
Thanks bluetone for sharing the answer with everybody else doing the quiz.
Will keep a look out for the rest of the #
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