First we'll deal with the ends. I assume that you know the area of a circle is .

The outside of the pipe has radius 27.5. So the area of this cross section, if it were a whole circle, would be . However there's a whole in this circle with radius 25, ie with area . Subtracting the smaller area from the larger one will give you the surface area of the end of the pipe, remember to multiply by two as there are two ends!

As for the outside and inside of the pipe, we'll do this in a very similar way.

The formula for the circumference of a circle is . Therefore the circumference of the larger circle would be . Now imagine if you cut the pipe down along it's length and unrolled it, you would have a rectangle with the circumference of the circle as the width, and the length obviously as it's length. Multiply the circumference of the larger circle by the length of the pipe to find the surface area of the outside of the pipe.

Repeat this for the inside using the smaller radius.