Follow these steps in this training problem: $1.$ Draw a picture of the ladder, in profile. A nice way to draw it is the ladder forms a triangle with the $90$ degree angle at the origin. Label things that are changing with action arrows, and name your variables. $2.$ Write an equality relationship between your variables. We don't care about the area of the triangle... $3.$ Differentiate with respect to time. Mind which things are constant. $4.$ Solve for the desired quantity. Someone has leaned a ladder precariously against a wall, and its sliding away, as in Figures $5$ and $6$ of your book, on page $200.$ The dimensions are different, though! The length of the ladder is $3\mathrm{.}8$ meters, and the top of the ladder is sliding down the wall at an alarming $1\mathrm{.}3$ meters per second. Calculate the rate at which the bottom of the ladder is sliding away from the wall when the top of the ladder is $2\mathrm{.}9$ meters from the floor. The bottom of the ladder is sliding away at meters per second.