**LESSON PLAN IN MATH**

**I. OBJECTIVES**

A. Discover the formula for the area of a triangles

B. Solve problems involving area of triangles

C. Work cooperatively in groups

**II. SUBJECT MATTER**

A. Area of Triangle

B. K to 12 Curriculum Guide pp.11-12

C. pictures, paper cut-outs, ruler, activity sheets, manila paper, overhead projector, laptop

D. Cooperation

**III. Procedure**

**A. Preparatory Activities**

**1. Review**

**Mystery Picture**

Ask the learners to give their prior knowledge about the person in the picture. Let them solve the area of the following quadrilaterals to know the name of person in the mystery picture. Choose the answers in the box.

**S= 3 m**

^{2 }I= 56 m^{2}R= 64 m^{2}C= 121 m^{2}U= 8 m^{2}**E= 28 m**

^{2}A= 15 m^{2}T= 12 m^{2}P= 120 m^{2}H= 12 m^{2}
__

__H____ ____I________P________P________A____ ____R____ ____C____ ____H_________U__________S____
5 4 7 7 3 6 8 5 1 2

Discuss that Hipparchus is the father of trigonometry. Relate that trigonometry is the study of measuring triangles.

**2. Motivation**

Ask:

*How well are you familiar with different triangles around you? Identify the following triangular objects shown in the following pictures.*
· Show pictures of triangular objects and let learners raise their hand if they know the object.

**B. Developmental Activities**

**1. Activity**

**Cooperative Learning**

· Divide the learners into groups with 4 members.

· Distribute the needed materials and activity sheets. Instruct pupils to read the directions carefully.

· Each group are will be provided paper cut-outs of quadrilaterals (parallelogram, rectangle, square)

· Using the ruler, each group will measure the dimension of the figures given to them and have them solve for the area.

· Once the students have found the area of each figure, they must create a diagonal line from bottom corner to top corner

· The learners must cut out their figures through the diagonals, creating two triangles.

· Remind the pupils on the proper decorum during group activity. Emphasize the importance of cooperation to successfully accomplish the task.

**2. Analysis**

· Each group will have a reporter to share their findings. Have them focus on the following questions:

a.

*What spatial figures are given to you?*
b.

*What is the area of each figure?*
c.

*What have you formed after cutting the figures into two through its diagonal?*
d.

*How does the area of the triangles compare to the areas of the original figure?***3. Abstraction and Comparison**

· Allow learners compare the area of the triangles to the area of their original figure.

· Let them discover that the area of a triangle is actually the half of the area of a parallelogram, rectangle or square.

· Guide them to derive the formula of the area of triangles from the formula of finding the area of a parallelogram which is base times height, divided by two ( or bh or (b x h) ÷ 2)

**4. Application**

· Using the derived formula let the learners solve the following problem.

**A paraw is a kind of sailboat with a triangular sail. If the sail measures 9 meters on its base and 8 meters in height, what is its area?**

· Relate to the learners that paraw is a local sailboat unique to Iloilo. An annual festival called Paraw Regatta is held every February. Ask the learners if they have experienced watching the festival.

· Let pupils analyze the problem using

**STAR Strategy**.**S-Search the Problem**

The paraw has a base of 9 meters and a height of 8 meters.

I can draw the triangle to picture it out.

I need to find the area.

**T-Translate the problem into an equation**

The formula for finding the area of a triangle is (b x h) ÷ 2. Therefore, (9 meters x 8 meters) ÷ 2.

**A-Answer the Problem**

A=

**(b x h) ÷ 2**
A= (9 m x 8 m) ÷ 2

A= 72 m

^{2}÷ 2
A= 36 m

^{2}or square meters.
The area of the paraw sail is 36 square meters.

**R-Review the Solution**

Since the area of a triangle is half the area of a parallelogram, twice the area should be equal to the product of base and height.

36 m

^{2 }= (9 m x 8 m) ÷ 2
36 m

^{2}x 2 = 9 m x 8 m
72 m

^{2}= 72 m^{2}
Provide other examples:

a.

*A triangular garden has a base of 12 meters and a height of 10 meters. What is its area?**b. Mang Lito plans to make a triangular table. The table measures 5 feet on its base and 4 feet in height. What is the area of the table?*

*c. The height of a triangular table cloth is 8 yards while its base is 6 yards. Find its area.*

**3. Generalization**

·

*How do we solve for the area of triangles?***IV. Evaluation**

Read the problem and show you solution.

1.

3.

*Give the area of triangle with the base of 9 cm and a height of 8 cm.*
4.

*What is the area of a triangular mirror if its base is 12.5 inches and its height is 7.2 inches?*
5.

*A triangular lawn measures 3 feet on its base while 5 feet in height. Find its area.*

*Prepared by:*

*Jaylord S. Losabia**Teacher III**A. Bonifacio Integrated School*