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7th grade · Math · Unit 18 of 18

Area & Constructions

Triangles, parallelograms and bisectors

What your child practices

Area of triangles and parallelograms using base and height, and the vocabulary of perpendicular and parallel lines and bisectors.

Alabama Course of Study content standard: 7.18; 7.22 · constructing perpendicular and parallel lines and bisectors, and areas of triangles and parallelograms

How we explain it

Children can open this short lesson before they practice.

  1. Triangle area = base × height ÷ 2. Parallelogram area = base × height.
  2. Perpendicular lines meet at 90°. A bisector cuts something exactly in half.
  3. Use a compass and straightedge to construct them.

Example: A parallelogram has a base of 9 cm and a height of 4 cm. What is its area? Area = base × height. 9 × 4 = 36. Answer: 36 cm²

Area & Constructions in Alabama

In the Alabama Course of Study, this is unit 18 of 18 in 7th grade Math, after Scale Drawings.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alabama State Department of Education (ALSDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Two lines that are always the same distance apart and never meet are…

    • intersecting
    • perpendicular
    • bisectors
    • parallel

  2. Question 2

    A triangle has an area of 30 cm² and a base of 6 cm. What is its height, in centimeters?

    • 14
    • 9
    • 10

  3. Question 3

    A triangle and a rectangle have the same base and the same height. How do their areas compare?

    • They are equal
    • The triangle's area is a quarter of the rectangle's
    • The triangle's area is half the rectangle's
    • The triangle's area is double the rectangle's

  4. Question 4

    A parallelogram has a base of 11 cm, a height of 3 cm and a slanted side of 5 cm. What is its area, in square centimeters?

    • 27
    • 33
    • 43

  5. Question 5

    Two lines meet at a 90° angle. They are…

    • parallel
    • perpendicular
    • equal
    • angle bisectors

  6. Question 6

    What is the height of a triangle?

    • The length of its shortest side
    • The distance around the triangle
    • The length of its longest side
    • The straight distance from the base to the opposite corner, at a right angle to the base

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