Grade 5 · Unit 5: Using units of measurement

Area of triangles and parallelograms

Cut and rearrange.

Land plots

Not all fields are rectangles. Some are triangles or parallelograms. We can find their areas by cutting and rearranging.

Parallelograms

Cut off a triangle from one side. Move it to the other side: it makes a rectangle. Area = base × perpendicular height.

Triangles

Two identical triangles make a rectangle (or parallelogram). So a triangle’s area = ½ × base × height. Base 8 cm, height 5 cm: ½ × 8 × 5 = 20 cm².

Compound areas

Split the shape into rectangles and triangles. Find each area. Add them together.

Irregular shapes

For a curved shape, count the whole squares. Then count the squares that are about half covered and halve the count. Choose the formula that fits: rectangle l × w, triangle ½ × b × h, or counting for curvy shapes.

What I learnt

• I can find the area of a parallelogram.
• I can find the area of a triangle.
• I can find areas of compound shapes.