2012 AMC 12B Problem 9
Problem 9 of 25EasierAlgebra
It takes Clea seconds to walk down an escalator when it is not operating, and only seconds to walk down the escalator when it is operating. How many seconds does it take Clea to ride down the operating escalator when she just stands on it?
Answer choices
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Solution
Let be Clea’s walking rate and the escalator’s rate, with the length equal to Walking on the moving escalator gives so
Standing takes time with so and seconds.
Thus, the correct answer is B.