| Problem: A ladder 10 meters long is leaning against a vertical wall with its other end on the ground. The top end of the ladder is sliding down the wall. When the top end is 6 meters from the ground is sliding at 2m/sec. How fast is the bottom moving away from the wall at this instant? |
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Mathematically, the ladder problem is almost identical to the circle problem that we did earlier. The extra feature is that it's a story problem. We have to draw a picture and think about the variables to see that $x^2 + y^2$ is a constant.