Area of a Triangle

Two identical triangles make a parallelogram: area = base × height ÷ 2

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About This Practice

One triangle is awkward to measure — but two identical triangles join into a parallelogram. The parallelogram is twice the triangle, so the triangle’s area = base × height ÷ 2. Tap “Rotate & join” to watch the second triangle make a half-turn and lock in, revealing where the ÷2 comes from.

Tap “Rotate & join”: a second identical triangle turns a half-turn and joins the first into a parallelogram. The parallelogram is twice the triangle, so the triangle's area is base × height ÷ 2.

MediumEstimated Time: 10mintriangle arearotate & joinparallelogrambase × height ÷ 2

How to Play

  1. Look at the triangle: find its base and height.
  2. Tap “Rotate & join” and watch the second identical triangle turn a half-turn.
  3. Check the parallelogram they form: same base and height as the original?
  4. Compare: how many times the triangle is the parallelogram?
  5. Write the formula: triangle area = base × height ÷ 2, and explain the ÷2.

Learning Objectives

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