1. Lesson Plan in Mathematics 3
Lesson 80 Area of a Rectangle and a Square
Date:
Time:
Time:
Objective
1. Derive the formula for the area of a rectangle and a
square
2. Find the area of a rectangle and square in square
centimeter and square meter
Value Focus
Decisiveness
Prerequisite Concepts and Skills
1. Multiplying whole numbers
2. Measuring length using centimeter and meter
3. Finding the area of a region bycounting square units
4. Unit of measure for area
Materials
Square grid, tape measure, crayons, and activitysheets
Instructional Procedures
A. Preliminary Activities
1. Drill
Show the following shapes. Let the pupils name the
shapes and tell the number of its sides.
Flash cards and let pupils answer mentally. e.g.
a. 15 50 f. 500 100
b.120 20 g. 3 000 100
c. 200 10 h. 1 500 100
d.180 100 i. 8 300 100
e. 500 20 j. 16 000 100
Answer Key:
a. 750 b. 2 400 c. 2 000 d.18000 e.10000
f.5 g. 30 h. 15 i. 83 j. 160
2. Review
Call pupils to convert the following measurements to
the indicated unit of measure:
a. 300 cm=_____m (3) d. 6 000cm =______m (60)
b. 10m=_____cm (1000) e. of 800 cm = ______ m (6)
c. 5 m = ______cm (550)
3. Motivation
1 cm
1 cm
What canyou say aboutthe illustration?
What does it show?
B. Developmental Activities
1. Presenting the Lesson
Let pupils identify the shapes given in Motivation and
let them explain why they say it is a square or a
rectangle.
Say:
Onesmallsquareinsidethe square/rectangleisequal
to 1 square unit. The number of square units that
covers the region/surface of the rectangle/square is
called its AREA.
Ask: What is the area of each figure?
How did you get the area of each figure? (Expected
answer: Count the number of small squares)
Let them identify the length and width of each figure.
Say and show: The column is referred to as length
and the row is referred to as width. Ask pupils to write
the measures of the length and width of each figure.
Ask:
What is the relationship of the length and width to the
area? (the product of the length and width is equal to
the area)
How can we get the area of a rectangle? Area of a
rectangle = length x width
= l x w
Say: Look at the measures of the length and width of
the square figures, what can you say about them?
(they are equal)
Say: For squares,length(column)andwidth(row)are
referred to as sides
Ask: How can we get the area of a square? Area of a
square = side x side
= s x s
Say: If the length of one small square is equal to 1
cm, what is the area of each figure?
Using the figures in Motivation, guide the pupils to
complete the table below.
Figure Length
(in cm)
Width
(in cm)
Area
Formula
square = s x
s
Area
(in sq. cm)
A 2 cm 7 cm Area of
rectangle =
l x ws
Area = 2 cm x 7
cm = 14
sq. cm
B
C
D
Answer Key:
B 4 cm 4 cm Area of
square = s x
s
Area = 4 cm x 4 cm
= 16 sq. cm
C 3 cm 3 cm Area of
square = s x
s
Area = 3 cm x 3 cm
= 9 sq.cm
D 4 cm 3 cm Area of
rectangle
= l x w
Area = 4 cm x 3 cm
= 12 sq.cm
2. 2. Performing the Activity
Ask:What are the standardunits of areameasure that we have
alreadylearned?
Let the pupils do the following activities in groups. Provide
them with the activity sheet, tape measure or ruler or
meter stick and the materials needed. Let them find the
area of the given objects by completing the table and
answering the questions provided.
Note: You mayuse other materials available. Draw the square
(2 m by 2m) inside the room using masking tape before
the start of the lesson or the daybefore.
Groups 1 and 2
Materials: Activity sheet, tape measure, piece of cloth or
Manilapaper(1m by 2 m), notebook(15 cm by20 cm),ID
card (8 cm by12 cm)
Measurethelength and the width of each object then fill in the
table.
Object Shape
of
object
Length Weight Formula Area
Cloth
Notebook
ID card
Questions:
a. What is the length of the cloth in meter?
b. What is the width of the cloth in meter?
c. Compute for the area in square meter.
d. What is the length of the notebook in centimeter?
e. What is the width of the notebook in centimeter?
f. Compute for the area in square centimeter.
g. What is the length of the handkerchief in centimeter?
h. What is the width of the handkerchief in centimeter?
i. Compute for the area in square centimeter.
3. ProcessingtheActivities
Let each group present their outputs. Let them discuss
how they get the area of each object given.
Ask: Howdo we get the areaof a rectangularfigure? How
about the area of a square figure?
4. Reinforcing the Concept
Let pupilsdo Activity 1 individually. Afterwards, callpupils
to share their answersandreasons
Let pupilsanswerthe followingproblems.Pupilscanwork
with theirpartners. After the pairs solve oneproblem,
discusstheirsolutionandanswers. Do this to the next
problem.
1. Findthe areaof a squarewith side15 cm.Write the
solutionor formulaandthen solve for the area.
Solution.A = s x s
A = 15cm x 15 cm = 225sq. cm
2. A rectangulargardenhasanarea of 24 sq. m. If its
lengthis 6 m, what is its width?
Ask pupilsto give the given facts. Thenletthem write the
solutionor formula.Let them solve for the missingwidth.
Given: A = 24 sq. m length=6m width=?
By substitution, A = l x w
24 sq. m = 6 metersx width Width = 24 sq. m ÷ 6 meters
Width = 4 meters
Formoreactivities let pupilsdoActivity 1 inLM.
Afterwards, discussandshare theiranswersand
solutions.
Answer Key:
A. 1) 14sq. m 2) 36 sq. m 3) 1 600sq. cm 4)2 500 sq. cm
5) 24 sq. m
B. 1) 3 m 2) 10cm by3 cm or 6 cm by5 cm or15 cm by 2
cm 3)256 sq. cm 4) 7 m
5. Summarizing theLesson
How do we find the area of a rectangle?
In finding the area of a rectangle, use
Area = length width or
Area = l x w
How do we find the area of a square?
In finding the area of a square, use
Area = side side or
Area = s x s
6. Applying to New and Other Situations
For more exercises let the pupils do Activity2 and 3 in the
LM. Afterwards, discuss and share their answers and
solutions.
Answer Key: Activity 2:
1) 48 sq. cm
2) 12 cm
3) Theyare equal; their areas are both 144 sq. m
4) 12 sq. m
C. Evaluation
Let pupilsdo Activity 4 in the LM individually.Answer Key:
1) 84 sq. cm
2) 9 m
3) 16 sq. cm
4) 12 sq. m
D. Home Activity
Let pupils answer Activity5 in the LM. Answer Key:
1) 9 sq. m 2) 6 sq. m 3) 16 sq. m
4) 24 sq. m 5) 4 sq. m 6) 25 sq. m
