Math CentralQuandaries & Queries


Question from Corey:

Walking up a broken escalator (escalator not working) takes 75 seconds. Riding up the same escalator (not walking) when it is working takes 45 seconds. How long would it take a person to walk up the escalator when it is working ?


  1. When you are walking up you go a distance of 1 floor in 75 seconds so your speed is 1/75 (one floor every 75 seconds).

  2. When you are riding up, your speed is 1/45.

  3. When you are walking up an operating escalator, your speed is combined: 1/45 + 1/75.

  4. Remember that time = distance/speed. The distance is still 1 floor. So t = 1 / (1/45 + 1/75). Calculate t.

Stephen La Rocque.

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