Area of Triangles & Parallelograms · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Area of Triangles and Parallelograms

Mathematics · Measurement · ages 10-11
Name ______________________   Date ____________

  1. A parallelogram has base 10 cm and height 6 cm. What is its area in square centimetres?

    Answer: ______________

  2. A parallelogram has base 8 cm and height 5 cm. What is its area in square centimetres?

    • 13
    • 40
    • 26
    • 45

  3. Which formula gives the area of a parallelogram?

    • A = b + h
    • A = b × h
    • A = 2 × b × h

  4. A triangle's area is always half the area of a matching parallelogram with the same base and height.

    Circle one:   True   False

  5. A triangle has base 9 cm and height 8 cm. What is its area in square centimetres?

    Answer: ______________

  6. Mia says the area of a parallelogram with base 6 cm and height 4 cm is 10 cm². What did she do wrong?

    • She added the base and height instead of multiplying
    • She used the wrong height
    • She forgot the units

  7. A triangle has base 12 cm and height 7 cm. What is its area in square centimetres?

    • 19
    • 84
    • 42
    • 31

  8. Sue says triangle area is base plus height, then halved: (9 + 8) / 2 = 8.5 for a 9 by 8 triangle. Is Sue right?

    Circle one:   True   False

  9. Ravi finds a triangle's area as base × height, without halving. For base 10 cm and height 6 cm, what does he get, and is it right?

    • 30 cm², correct
    • 60 cm², correct
    • 60 cm², too big (real area is 30 cm²)

  10. Why is triangle area half of the related parallelogram?

    • Two identical triangles fit exactly into the parallelogram
    • Triangles are always smaller
    • Halving makes numbers tidy
    • The height is always doubled
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Area of Triangles and Parallelograms W1-mt_ML5t7n2-U8-s1

  1. 60 · The area is 60 square cm because 10 times 6 equals 60.
  2. 40 · 40 square cm is correct because base times height is 8 times 5.
  3. A = b × h · For a parallelogram, multiply the base by the height.
  4. True · Two identical triangles make that parallelogram, so one triangle is half of it.
  5. 36 · The area is 36 square cm because half of 9 times 8 is 36.
  6. She added the base and height instead of multiplying · 6 + 4 = 10, but area needs multiplication: 6 × 4 = 24 cm².
  7. 42 · 42 square cm is correct because half times 12 times 7 equals 42.
  8. False · Sue is wrong. Triangle area multiplies: half of 9 times 8 is 36, not 8.5.
  9. 60 cm², too big (real area is 30 cm²) · Without halving, Ravi's answer is double the true area. The correct area is half of 10 × 6, which is 30 cm².
  10. Two identical triangles fit exactly into the parallelogram · Two identical triangles fit exactly into the parallelogram, so each covers half.
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