Worked Example 1
Half of a Rectangle
A right triangle has legs of 6 units and 8 units. Find its area.
- 1Two copies of the triangle make a 6-by-8 rectangle with area 6 × 8 = 48.
- 2The triangle is half: 48 ÷ 2 = 24
Answer: 24 square units
Florida Grade 6 Math · Geometric Reasoning
MA.6.GR.2.1: Area of Triangles
What this Grade 6 benchmark means, worked examples, common mistakes, and a free printable worksheet.
Created by a Florida mom · Published by Tropical Learning LLC
What Is Benchmark MA.6.GR.2.1?
A right triangle is half of a rectangle, so its area is half the rectangle's area. That leads to the formula for the area of any triangle: A = 12 × base × height. Students should know this formula from memory.
The height is the perpendicular distance from the base to the opposite vertex, not the length of a slanted side.
Official benchmarkDerive a formula for the area of a right triangle using a rectangle. Apply a formula to find the area of a triangle.
On the FAST test: part of the Grade 6 reporting category Geometric Reasoning, Data Analysis, and Probability, which is about 25–36% of the test.
Worked Examples
Worked Example 2
Using the Formula
A triangle has a base of 10 cm and a height of 7 cm. Find its area.
- 1A = 12 × 10 × 7
- 212 × 10 × 7 = 35
Answer: 35 square centimeters
Common Mistakes to Watch For
Forgetting to take half
Wrong:Base 10, height 7: area = 70
A triangle is half of a rectangle: 12 × 10 × 7 = 35.
Using a slanted side as the height
Wrong:Using the 9-inch slanted side as the height of a triangle
The height must be perpendicular (at a right angle) to the base.
Helpful Math Tip
Cut a paper rectangle along its diagonal to see two identical right triangles. That is the whole reason for the 12.
Related Grade 6 Skills
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