A ladder 5 m long is leaning against a wall. The bottom of the ladder is pulled along the ground, away from the wall, at the rate of 2cm/s. How fast is its height on the wall decreasing when the foot of the ladder is 4 m away from the wall ?

Explanation

To solve the problem, we will follow these steps:

### Step 1: Understand the problem and set up the diagram
We have a ladder of length 5 m leaning against a wall. The distance from the wall to the foot of the ladder is denoted as \( x \), and the height of the ladder on the wall is denoted as \( h \).

### Step 2: Use the Pythagorean theorem
Since the ladder, wall, and ground form a right triangle, we can apply the Pythagorean theorem:
\[
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