Grades Sixth Grade GeometryArea of Triangles & Composite Figures

Area of Triangles & Composite Figures

📐 Geometry

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Area of Triangles & Composite Figures

Decompose complex shapes into simpler pieces you already know.

The area of a triangle is half the area of a parallelogram with the same base and height. For composite figures (irregular shapes made of simpler polygons), decompose the shape into rectangles, triangles, and other familiar shapes, find each area separately, then add (or subtract) them.

A_{\triangle} = \frac{1}{2} \times b \times h

Key Measurement Rules

Base (b): any side of the triangleHeight (h): perpendicular distance from base to opposite vertexHeight is always perpendicular — it forms a 90° angle with the baseFor obtuse triangles, height may fall outside the triangle

Always double-check that height is perpendicular, not a slant side.

🏠Composite Figure

An L-shaped floor: Break into two rectangles. Rectangle A: 8m × 4m = 32 m². Rectangle B: 3m × 5m = 15 m². Total area = 32 + 15 = 47 m².

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Remember This!

For composite figures, you can also find the area of the large enclosing rectangle and subtract the missing pieces. Both methods give the same answer.

✏️ Try It!

A right triangle has a base of 10 cm and a height of 6 cm. What is its area?

Practice with CalcVerse

📏Perimeter & Area ⬡Polygon Angle Explorer

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