1. SEMI-DETAILED LESSON PLAN
IN MATH III (GEOMETRY)
SUBJECT MATTER: AREA
I. OBJECTIVES:
1. define area
2. find the area of different polygons and circles
3. solve real life problems involving areas
4. manifest cooperation in group work
II. DEVELOPMENT OF THE LESSON
A. MOTIVATION
A fairy tale will be told.
Once upon a time in a faraway land named the Land of Closed Figures, there
lived a very handsome yet just an ordinary man named Aare. He already lost his
parents, that’s why he decided to travel and leave his home. He traveled and traveled
until he reached a great kingdom. He entered into it and saw a beautiful princess. He
went near her and noticed that the princess was crying. He then asked for her name
and the reason why she’s crying. The latter said her name is Princess Polygon and
that she’s crying because her parents, King Base and Queen Height, were cursed by a
witch and that the only way to regain them is for her to give the area of their land. She
then showed a sketch of their land.
3 km
5 km
Aare helped Princess Polygon solve the problem and they were able to regain
her parents. Because of the king’s and queen’s rejoice they let Aare marry the
princess and the couple lived happily ever after.
2 km

2. B. DISCUSSION
1. The class will be divided into five groups.
2. The teacher will distribute sheets containing what area is all about and the formulas
for finding the areas of polygons and circles.
AREA
The amount of surface in a region is its area. The area of any two
dimensional figure can be determined by imagining its surface completely filled
with square regions called square units.
A square whose side is one unit long has an area of one square unit.
1 cm The figure at the left represents 1 square cm or 1 cm2
.
1 cm
To illustrate the meaning of area, consider a rectangular region whose
length measures 4 units and whose width measures 3 units. How many square
units are there in its surface?
3 units
4 units
By counting, there are actually 12 units, and 12 is the product of 4 and 3.
Thus, the rectangular region has 12 square units in its surface.
FORMULAS FOR FINDING THE AREA
AREA OF A RECTANGLE = LENGTH X WIDTH
= l x w
AREA OF A SQUARE = SQUARE OF THE SIDE
= s2
AREA OF A PARALLELOGRAM = BASE X HEIGHT
= b x h
AREA OF A TRIANGLE = ½ (BASE X HEIGHT)
= ½ (b x h)
AREA OF A TRAPEZOID = ½ X HEIGHT X (BASE1 + BASE2)
= ½ h(b1 + b2)
AREA OF A CIRCLE = π X SQUARE OF RADIUS
= πr2

3. 3. The groups will be given time to come up with the solution to the princess’
problem.
4. Using the Manila paper provided, the groups will writhe their solution and post it on
the board. Reporting will follow.
5. After all the groups have presented their output, the teacher will show Aare’s
solution and compare it with the groups’ solutions. The class will be encouraged to
comment and ask questions.
AARE’S SOLUTION:
AREA OF LAND = AREA OF CIRCLE + AREA OF RECTANGLE
= πr2
+ (l x w)
= 3.14 ( 1 km )2
+ ( 5 km X 3 km)
3 km
=3.14 km2
+ 15 km2
5 km = 18.14 km2
6. This problem will be given for the groups to solve.
The Alonzos want to plant Bermuda grass in their new backyard. The diagram of
the yard, the patio and the flower garden is shown below. How many square meters of
Bermuda grass is needed for the yard?
6 m
4m
11 m
2m
21 m
If necessary, additional examples will be given.
2 km
patio
yard
garden

4. III. EVALUATION
DIRECTION. Read the problems carefully. Choose the best answer. Use π = 3.14.
1. Find the area of a parallelogram with h = 4.6 cm, b = 8.8 cm.
a. 30.48 cm2
b. 31. 48 cm2
c. 40.48 cm2
d. 41.48 cm2
2. Find the area of a trapezoid with b1 = 5 m, b2 = 2.5 m. and h = 4 m.
a. 10 m2
b. 15 m2
c. 20 m2
d. 25 m2
3. What is the area of a square with a side that measures 325 mm?
a. 105,625 mm2
b. 106,625 mm2
c. 107,625 mm2
d.108,625 mm2
4. What is the area of a circle whose radius measures 0.08 m?
a. 0.01 m2
b. 0.02 m2
c. 0.04 m2
d. 0.06 m2
5-6 What is the area of the given figure?
5.
12 m a. 56 m2
c. 112 m2
b. 66 m2
d. 132 m2
5 m 6 m
6.
a. 34.54 cm2
c. 379.94 cm2
b. 69.08 cm2
d. 1519. 76 cm2
7. A rectangular photo album is 28 cm long and 17 cm wide. What is the area of the
photo album?
a. 238 cm2
b. 338 cm2
c. 476 cm2
d. 576 cm2
8. The radii of two circles are 10 cm and 11 cm. By how many square cm is the area of
the larger circle greater than the area of the smaller circle?
a. 55.94 cm2
b. 65.94 cm2
c. 75.94 cm2
d. 85.94 cm2
Prepared by:
JIZON U. MORANTE
22 cm