Lesson 3: Determine the Area of Trapezoids6.GR.1

I can…

I can find the area of a trapezoid using the formula A = ½(b1 + b2) × h.

Key words

• Area of Trapezoids — Add the two bases, halve it, then multiply by the height.
• Trapezoid — A shape with four sides and just one pair of parallel sides.
• Parallel — Lines that stay the same distance apart and never meet.
• Base 1 (b1) — A side of a trapezoid. It is one of two parallel sides.
• Base 2 (b2) — A side of a trapezoid. It is the other parallel side.
• Height — How tall it is, measured straight up from the base.
• Perpendicular — Lines that meet at a square corner (90°).
• Area — How much flat space a shape covers.
• Decompose — Break a number or shape into smaller parts.
• Right trapezoid — A trapezoid with two square corners.

Steps

1. My trapezoid window has a top base of 4 feet, a bottom base of 8 feet, and a height of 5 feet.
2. I write the formula: A = ½ × (b1 + b2) × h.
3. I add the bases first: 4 + 8 = 12.
4. I multiply by the height: 12 × 5 = 60.
5. I take half: ½ × 60 = 30. So the area is 30 square feet.

Try it

A garden bed shaped like a trapezoid has bases of 7 feet and 3 feet, and a height of 4 feet. What is its area?

Check your answer

20 sq ft

A = 1/2 x (b1 + b2) x h = 1/2 x (7 + 3) x 4 = 1/2 x 10 x 4 = 20 square feet.

Sentence starter

I know ___ because ___.

Goal: I can explain my steps using the words trapezoid, base, height, and area.