Area of Rectangles & Triangles (Grades 5–6)
Area is the space inside a shape, measured in square units. A rectangle's area is length × width. A triangle is exactly half of the rectangle that would surround it, so its area is ½ × base × height. The height must be the straight-up distance, perpendicular to the base.
Understanding area of rectangles & triangles
Area is the space inside a shape, measured in square units. A rectangle's area is length × width. A triangle is exactly half of the rectangle that would surround it, so its area is ½ × base × height. The height must be the straight-up distance, perpendicular to the base.
Key Idea
Area is the space inside a shape, measured in square units. A rectangle's area is length × width. A triangle is exactly half of the rectangle that would surround it, so its area is ½ × base × height. The height must be the straight-up distance, perpendicular to the base.
Seeing it in action
Worked example
Area of a triangle with base 6 and height 4?
½ × base × height = ½ × 6 × 4 = 12 square units.
A triangle is half of its surrounding rectangle.
Try a few
Rectangle 5 by 3 — area?
Triangle base 10, height 4 — area?
Rectangle 7 by 7 — area?
Perimeter Patrol
A calm tile-grid game for building and reading area and perimeter.
Ready for the interactive lab?
Practice area of rectangles & triangles in Numeris with instant feedback.
Put the reasoning on paper.
Try six fraction, angle, perimeter and area questions with explained answers, for grades 4–6.
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