Grade 5 · Spatial Sense · Area of Parallelograms and Triangles
Build Area Formulas
Area formulas are shortcuts that come from spatial relationships. Rearranging a shape explains each formula.
The big idea
Base and perpendicular height determine area
A parallelogram can be rearranged into a rectangle with the same base and height. Two matching triangles form a parallelogram.
Work it through
Find the area when b = 8 cm and h = 5 cm
- 1. Parallelogram: A = b × h = 8 × 5 = 40 cm².
- 2. Triangle: A = (b × h) ÷ 2.
- 3. A = (8 × 5) ÷ 2 = 20 cm².
- 4. Use the perpendicular height, not a slanted side.