An iron pipe 20 cm long has exterior diameter equal to 25cm. If the thickness of the pipe is 1cm, find the whole surface of the pipe.

Explanation

To find the whole surface area of the iron pipe, we will follow these steps:

### Step 1: Identify the given dimensions
- Length of the pipe (h) = 20 cm
- Exterior diameter of the pipe = 25 cm
- Thickness of the pipe = 1 cm

### Step 2: Calculate the exterior radius
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