Lesson: Intermediate Problem Solving - 06t03

Estimating — Rates

[Page 6 of 27]

Our strategy of establishing a logical range for correct answers, then eliminating choices outside of that range, also works well on rate problems (and particularly well on combined-rate problems). Let's consider an example.


Steve gets on an elevator at the 11th floor of a building and rides up at a rate of 57 floors per minute. At the same time Joyce gets on an elevator on the 51st floor of the same building and rides down at a rate of 63 floors per minute. If they continue traveling at these rates, at which floor will their paths cross?
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Choose estimations for each rate that will make it easier to estimate a solution range for the problem. Fill in the Text Boxes below with your estimates, and then click Continue.
  • Steve gets on an elevator at the 11th floor of a building and rides up at a rate of floors per minute.
  • Joyce gets on an elevator on the 51st floor of the same building and rides down at a rate of floors per minute.

Because the rates in the question stem are quite close, estimating that they are equal is a good strategy, and 60 is right in between the two rates.

It's important to keep in mind however, that Joyce is moving a bit faster than our estimate of 60, while Steve is moving a bit slower.

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