<h3>Area of common shapes</h3><ul><li>Rectangle: <code>A = length x width</code></li><li>Triangle: <code>A = ½ x base x height</code></li><li>Parallelogram: <code>A = base x height</code></li><li>Circle: <code>A = πr²</code> (use π ≈ 22/7 or 3.142)</li><li>Sector: <code>A = (θ ÷ 360) x πr²</code></li></ul><h3>Surface area from nets</h3><p>A <strong>net</strong> is a flat layout of all the faces of a solid. The <strong>surface area</strong> is the sum of the areas of these faces. A closed cylinder has two circles plus a rectangle that wraps around: <code>SA = 2πr² + 2πrh</code>.</p><h3>Irregular shapes</h3><p>For an <strong>irregular shape</strong> on a grid, count whole squares, then add roughly half for the part-squares to estimate the area.</p><div class="callout"><strong>Kenyan context:</strong> A circular cattle dip in Narok has a radius of 7 m. Its surface area of water is <code>πr² = (22/7) x 7 x 7 = 154</code> square metres. A triangular plot with base 30 m and height 20 m has area <code>½ x 30 x 20 = 300</code> square metres.</div>