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Year 8 Maths — Area of triangles and parallelograms

Find the area of a parallelogram, a triangle and a rhombus, and the perimeter of a straight-sided shape.

Name: ________________________

  1. 1.Sort each rule by what it works out.

    Groups: Area · Perimeter

    • base × height
    • 1/2 × base × height
    • 4 × side
    • all the sides added together
    • 2 × (length + width)
    • length × width

  2. 2.A triangle and a parallelogram share the same base and the same height. The triangle's area is...

    • a) twice the parallelogram's area
    • b) half the parallelogram's area
    • c) impossible to compare
    • d) the same as the parallelogram's area

  3. 3.A triangle has a base of 9 cm and a height of 4 cm. What is its area, in square centimetres?

  4. 4.A parallelogram has an area of 60 square centimetres and a base of 10 cm. What is its height, in centimetres?

  5. 5.A triangle has an area of 24 square centimetres and a base of 8 cm. What is its height, in centimetres?

  6. 6.Every one of these triangles has a height of 6 cm. Match each base to the triangle's area in square centimetres.

    • base 4 cm
    • base 5 cm
    • base 8 cm
    • base 10 cm
    • 15
    • 30
    • 24
    • 12

  7. 7.A rectangle 14 cm by 9 cm has a triangle of base 14 cm and height 9 cm cut out of it. What area is left, in square centimetres?

  8. 8.A rhombus has diagonals of 8 cm and 6 cm. What is its area, in square centimetres?

Answer key — Year 8 Maths — Area of triangles and parallelograms

  1. 1. base × height → Area; 1/2 × base × height → Area; 2 × (length + width) → Perimeter; 4 × side → Perimeter; length × width → Area; all the sides added together → Perimeter
  2. 2. b) half the parallelogram's area
  3. 3. 18
  4. 4. 6
  5. 5. 6
  6. 6. base 4 cm → 12; base 5 cm → 15; base 8 cm → 24; base 10 cm → 30
  7. 7. 63
  8. 8. 24