Determine the Area of Triangles

6.GR.1 · Unit 5 · Lesson 2

Name   Period

Objectives / Objetivos

Content Objective: I can find the area of a triangle using the formula A = ½ × base × height.

Language Objective: I can explain my steps using the words base, height, area, and perpendicular.

Key Idea / Idea clave

Area of Triangles. Formula: Area = ½ × Base × Height (A = ½ b · h). 1. Identify the base and the perpendicular height to that base. 2. A triangle is exactly half of a rectangle with the same base and height. 3. Multiply base by height, then divide by 2

I Notice / Observo

  • What shape are the garden beds?
  • What measurements do we need to find the area?

I Wonder / Me pregunto

  • Why do we divide by 2 when finding the area of a triangle?

Vocabulary / Vocabulario

Term / TérminoDefinition / Definición
Area of a Triangle
Área de un triángulo		The space inside a triangle. A triangle is half of a rectangle with the same base and height, so A = ½ × b × h.
El espacio dentro de un triángulo. Un triángulo es la mitad de un rectángulo con la misma base y altura, por eso A = ½ × b × h.
Base
Base		Any side of a triangle can be the base. Once you pick a base, the height must be measured perpendicular (at a 90° angle) to it.
Cualquier lado de un triángulo puede ser la base. Una vez que eliges la base, la altura debe medirse perpendicular (en un ángulo de 90°) a ella.
Height
Altura		The straight-up distance from the base to the top corner.
La distancia recta desde la base hasta la esquina de arriba.
Area
Área		How much space is inside a flat shape.
Cuánto espacio hay dentro de una figura plana.
Perpendicular
Perpendicular		Two lines that meet to make a square corner (90 degrees).
Dos líneas que se unen formando una esquina recta (90 grados).
Composite figure
Figura compuesta		A shape made by putting two or more simple shapes together.
Una figura formada al juntar dos o más figuras simples.

Practice Preview / Vista previa de práctica

  1. What is the area of a triangle with base 10 cm and height 6 cm?
    1. 30 sq cm
    2. 60 sq cm
    3. 16 sq cm
    4. 30 cm
  2. Problem 2
  3. Match each shape to its area. Watch the rule: triangles use A = ½ × base × height, but parallelograms and rectangles use A = base × height (do NOT take half).
  4. Find the Area Error
    1. Step 1: Identify base and height — b = 14 m, h = 9 m
    2. Step 2: Write the formula — A = ½ × b × h
    3. Step 3: Substitute values — A = ½ × 14 × 9
    4. Step 4: Calculate — A = ½ × 23 = 11.5 sq m

    Which step has the mistake? Explain it and write the correct work.

Reflection / Reflexión

One thing I learned today / Una cosa que aprendí hoy: