1. The total surface area A exists of:

2 congruent right triangles which form a rectangle.(yellow)

2 rectangles (lightblue, green).

2. Unfortunately you didn't give us the dimension you have obtained by measuring

. So I called one side a and

**estimated **the missing length x as

.

Then the hypotenuse of the right triangle is

3. Use Pythagorian theorem to calculate the length of y:

4. Calculate the different areas:

The sum of these 3 areas yields the total surface area

5. If and only if you have measured a = 3 cm then the total area is indeed 48 cm².