Cogito
Grade 6 Math · Chapter 7 · Lesson 4
Area of a Trapezoid
Two copies make a parallelogram.
10 problems · about 18 minutes · 6.G.A.1
What this lesson teaches
The child finds the area of a trapezoid using the two parallel sides and the height.
- Two identical trapezoids make a parallelogram.
- Its base is the two parallel sides added together.
- Area = (a + b) × h ÷ 2.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Area of a Parallelogram: Base 8, height 7. Area?
Answer 56
Why 56 square units.
Review — Surface Area from Nets: A cube with edge 5. Surface area?
Answer 150
Why 150.
Review — Area of Triangles: Base 14, height 6. Area?
Answer 42
Why 42.
Warm Up
Straightforward practice. Get the method working first.
3 problemsParallel sides 5 and 11, height 4. Area?
Answer 32
Why 32 square units.
Parallel sides 3 and 7, height 2. Area?
Answer 10
Why (3 + 7) × 2 ÷ 2.
Parallel sides 6 and 6, height 5. Area?
Answer 30
Why Equal sides make it a parallelogram.
Build It Up
The same ideas with more to keep track of.
2 problemsParallel sides 2 and 8, height 4. Area?
Answer 20
Why (2 + 8) × 4 ÷ 2.
Why is the answer halved at the end?
Answer Two trapezoids were used to build the parallelogram.
Why Look at the two copies.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Garden Bed: Parallel sides 4 and 8, height 3. What is the area?
Answer 18
Why 18 square units.
The Roof Panel: Parallel sides 5 and 9, height 6. What is the area?
Answer 42
Why 42 square units.