posted by Sam .
A 13 foot ladder is resting against the wall. The bottom is initially 10 feet away from the wall and is being pushed towards the wall at a rate of 0.25 ft/sec. How fast is the top of the ladder moving up the wall 20 seconds after we start pushing? Hint: the hypotenuse (ladder) is a constant since the length of the ladder never changes.
This is what I think I start with: