6th grade · Math · Unit 13 of 19
Perimeter & Area
Triangles, parallelograms, trapezoids
What your child practices
Finding the perimeter of L-shapes and other polygons, and the area of triangles (b × h ÷ 2), parallelograms (b × h) and trapezoids ((a + b) × h ÷ 2), including working backwards to a missing measurement.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 6.8(B); 6.8(D) · area of parallelograms, trapezoids and triangles
How we explain it
Children can open this short lesson before they practice.
- Perimeter is the distance around. Add every side.
- Triangle area = base × height ÷ 2.
- Parallelogram area = base × height. Trapezoid area = (a + b) × height ÷ 2.
Example: A triangle has a base of 8 cm and a height of 5 cm. What is its area? 8 × 5 = 40. 40 ÷ 2 = 20. Answer: 20 cm²
Perimeter & Area in Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 13 of 19 in 6th grade Math, after Angles & Triangles and before Volume & Capacity.
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: Texas Education Agency (TEA)
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
A parallelogram has an area of 77 cm² and a base of 7 cm. What is its height?
answer boxcm
11 cm
Hint: Area = base × height, so height = area ÷ base.
Question 2
A trapezoid has parallel sides of 8 cm and 14 cm, and a height of 2 cm. What is its area?
answer boxcm²
22 cm²
Hint: Add the parallel sides, multiply by the height, then divide by 2: (a + b) × h ÷ 2.
Question 3
A triangle has a base of 8 cm and a height of 8 cm. What is its area?
answer boxcm²
32 cm²
Hint: A triangle is half of a parallelogram with the same base and height, so area = base × height ÷ 2.
Question 4
A triangular sail has a base of 3 m and a height of 4 m. How much fabric covers the sail?
- 12 m²
- 6 m²
- 7 m²
- 14 m²
6 m²
Hint: Fabric covering a surface is an area question. Area of a triangle = base × height ÷ 2.
Question 5
Join the points in order, A to F, then back to A. Each grid square is 1 m long. What is the perimeter of the shape?
answer boxm
22 m
Hint: Add all 6 sides. Shortcut: the two short steps add up to the full width and height, so the perimeter equals the perimeter of the rectangle around the shape.
Question 6
A parallelogram has a base of 9 m, slanted sides of 14 m, and a height of 10 m. What is its area?
answer boxm²
90 m²
Hint: Area of a parallelogram = base × perpendicular height. The slanted side is not the height.