When the paper is folded, the shaded part is a triangle formed by the fold.

• From the figure, identify the dimensions marked on the shaded triangle.
• Area of shaded part = \(\frac{1}{2} \times \text{base} \times \text{height} = 40\) cm².
• Use the given dimensions to find the original length and breadth of the rectangle.
• Perimeter = 2 × (length + breadth) = 2 × (l + w) = 42 cm.

Final Answer: 42 cm