SCUSD Common Core Mathematics Lesson Planning Guide
Unit Title: Expressions
Lesson 5: Area of a Triangle
Approx. time:
1-2 days
(45 min per
day)
A. Focus and Coherence
Students will know…
 Triangles and polygons can be decomposed into
other shapes.
 A variable is an unknown term (number)
represented by a letter.
 Expressions can be equivalent, but look different
Ex: 2(x+3) is equivalent to 2x+6.
Students will be able to…
 Write expressions with variables, whole numbers,
and exponents and from real-world situations.
 Find the area of right triangles using the formula
A= (b x h) / 2.
 Language Function: Explicitly use vocabulary
(base, height, area, triangle, right angle, edge) to
explain and write the steps to find the area of a
triangle.
 Use the language stem to communicate effectively
while collaborating in teams:
1). I agree/disagree
because____________________.
Student prior knowledge:
 When to use order of operations
 Evaluate expressions with variables, whole
numbers, and exponents
 Area of rectangle
CCSS-M Standards:
Supporting Standard G.1; EE.2a
ELL Support: Explicit vocabulary instruction for the types,
components and measurement units of geometric figures.
B. Evidence of Math Practices
What will students produce when they are making sense,
persevering, attending to precision and/or modeling, in
relation to the focus of the lesson?
1. Make sense of problems and persevere in solving
them.
 Students will solve for the area using the
formula A=1/2 (b xh)
2. Reason abstractly and quantitatively.
3. Construct viable arguments and critique of others
4. Model with mathematics.
 Students will use/create hands on
manipulatives of triangles and have peers
find the area for the right triangles.
5. Use appropriate tools strategically.
6. Attend to precision.
 Students will use appropriate
measurement units and correct
terminology to justify reasonable
solutions.
7. Look for and make use of structure.
8. Look for and express regularity in repeated
reasoning.
Which math concepts will this lesson lead to?
 Equivalent expressions
 Use of real-world formula and perform arithmetic
operations in the correct order
Guiding Question(s)
1) How does what we measure influence how we measure?
2) How can space be defined through numbers and measurement?
3) How do you find the area of a square or rectangle?
4) How do you find the area of a triangle?
Formative Assessments
A. Checking for Understanding (CFU): Warm-Up—Students were able to use prior knowledge to find the area of a
rectangle or square.
Grade: 6
Unit: Expressions
Day: 5
B. CFU: THINK-WRITE-PAIR-SHARE—Collect students’ paper to determine student understanding or area of a
triangle.
C. CFU: Cut out triangles—collect students’ recorded papers.
Anticipated Student Preconceptions/Misconceptions
 Students can find the area of a rectangle, but not know how to find the area of a triangle.
Materials/Resources
Paper, pencil, laptop/computer, LCD projector, color pencil, poster paper
C. Rigor: fluency, deep understanding, application and dual intensity
What are the learning experiences that provide for rigor? What are the learning experiences that provide for evidence of
the Math Practices? (Detailed Lesson Plan)
Warm Up (25 minutes)
Intro: we’ve been studying formulas now we will look at triangles.
Students need experience in measuring squares and rectangles and calculating their areas. As a warm-up, have students
measure at least one square and one rectangle found within the classroom, record its dimensions, and calculate the area
of each. For example, they could measure floor tiles, windows, chalkboards, bulletin boards, desktops, shelves, and so
forth. Challenge them to measure as many different shapes as possible and report back to the class.
Divide students into groups of three. All three are responsible for the work, but the following tasks could be assigned:
Recorder: Keeps a record of all important information.
Measurement Verifier: Confirms all measurements and calculations.
Reporter: Shares all pertinent information with the class.
Allow students to share within their groups, and check the measurements and calculations before allowing them to
continue. If necessary, review the area formula for rectangles: A = b × h.
Material Needed: Ruler, paper, pencil
Lesson
Part 1
A. Begin the lesson by having students view a video on how to find the area of a triangle.
Before you show the video, be explicit and tell them that they will be need to be able to explain either in written
or illustration form, how to find the area of a right triangle.
B. http://learnzillion.com/lessons/1883-find-the-area-of-a-right-triangle rectangle square relationship (video is 4
min long)
C. After the video, ask students to THINK-WRITE individually. They are to explain in written or illustration form on a
piece of paper, how to find the area of a right triangle using a rectangle. (2min)
D. Next, PAIR-SHARE with a partner. Each partner will explain the steps of how to find the area of a right triangle.
Partners will need to use the language stem: I agree/disagree with ______________ because______________.
(6 min-10 min)
E. Once students have all shared, give students one minute to add or delete to their paper in a different color
(color pencils).
F. Put up a poster paper and label the center Area of a Triangle. Have student think about what they now know
about finding the area of a right triangle. Call on students to share out. Record their responses on the poster.
(5 min)
G. Next, ask students to work with their partners and come up with an expression for the area of a right triangle.
Grade: 6
Unit: Expressions
Day: 5
(IF during the share out, a student provides the formula for Area of a Triangle, then skip this part. Write the
formula up on the board and ask students think-pair- share about each part of the formula). Have an in depth
discussion about the formula and identify each component.
Area = ½ (b X h)
h
b
Materials Needed: Paper, pencil, laptop/computer, color pencil.
Teacher --LCD projector, chart/ poster paper
Part 2:
H. Have students cut up their own right triangles. They are to then find the area of the triangle using the formula
A = ½ (b x h). Once all students have solved and cut up their own triangles, they will then switch them with
another student. During this process, both students must sit and discuss whether their answers were correct or
incorrect. Students will switch with at least four other students. Students are to record down each of the
triangles they solved. By the end of this activity, they should have recorded down four different triangles and
solved them. (30 minutes)
I. Debrief with students what they learned from the activity.
Materials Needed: paper, scissor, ruler, pencil
Closure
Ticket-Out-the-Door
Find the area of the right triangles below.
1.
2.
5 cm
3.
8 in
10 yd
5 cm
4 in
12 yd
A = ____________________
A = ____________________
A = ____________________
Suggested Homework/Independent Practice
****Measure at least two triangles at home and solve them.
Grade: 6
Unit: Expressions
Day: 5