1. The problem is to understand the formulas for the perimeter and area of common plane figures. 2. The perimeter of a plane figure is the total length around the figure. It is found by adding the lengths of all its sides. 3. The area of a plane figure is the amount of space inside the figure. Different figures have different formulas for area. 4. For a rectangle with length $l$ and width $w$: - Perimeter $P = 2(l + w)$ - Area $A = l \times w$ 5. For a square with side length $s$: - Perimeter $P = 4s$ - Area $A = s^2$ 6. For a triangle with base $b$ and height $h$: - Perimeter $P = $ sum of all three sides - Area $A = \frac{1}{2} b h$ 7. For a circle with radius $r$: - Perimeter (circumference) $C = 2 \pi r$ - Area $A = \pi r^2$ 8. These formulas help calculate the boundary length and the space inside various plane figures easily.