Measures of Dispersion and Variability: Range, QD, AD and SD
Q4-MATH4-WEEK 2- LESSON 4- FINDING THE AREA OF TRAPEZOIDS.pptx
1.
2. Visualize the area
of a trapezoids
Derive the formula
for finding the area
of a trapezoids
Find the area of a
trapezoids
3. Answer as fast as you can.
12 x 5
234 x 25
120 x 13
25 x 8
14 x 6
4. Match the figures in Column A with their corresponding areas in Column
B. Choose the letter of the correct answer.
A B
5. Mr. Cruz cultivated a small garden
lot in the shape of a trapezoid.
The bases are 3 meters and 6
meters, while the distance
between the two bases is 4
meters. What is the area of the
lot? What is the shape of the
garden lot?
What is asked in the problem?
How are we going to find the
area of the garden lot?
5 m
6. To find the area of the garden lot, we
need to find the area of the trapezoid.
The lot has an
upper base of 3 meters
and a lower base of 5
meters.
Its height is 4 meters.
Base 1= 3 m
Base 2 = 5 m
Height = 4 m
7. Solution 1: By counting the whole squares
and squares partly inside the trapezoid.
1 2 3 4
5 6 7 8
9 10 1
1
1
2
1
3
14 1
5
1
6
The area of
the trapezoid
lot is 16 m².
8. Solution 2: By drawing or cutting a trapezoid which
is exactly the same as the original trapezoid and
then forming a parallelogram.
b1= 3
m
b2= 5
m
h= 4 m
b1= 3
m
b2= 5
m
We can say that the
base of the
parallelogram is the
sum of b1 and b2 of
the trapezoid.
Area= ?
One of the trapezoid
is ½ of the
parallelogram.
The area of the
trapezoid is ½ of the
area of the
Base = 8 m
9. The area of the
parallelogram can be solved
using the formula:
b1= 3
m
b2= 5
m
h= 4 m
b1= 3
m
b2= 5
m
Area= ?
Base = 8 m
A = b x h
= (b1 + b2) x h
= ( 3m + 5m) x
4m
= 8 m x 4 m
= 32 m²
The area
trapezoids:
A = 32 m² ÷
2
= 16 m
Therefore, the area of
the trapezoidal garden
lot is 16 m² .
10. b1= 3
m
b2= 5
m
h= 4 m
Area of trapezoid = (b1 +
b2) x h
To solve for the area of a
trapezoid, we use this
formula:
2
or
A = ½ (b1 + b2) x
h
11. 8 m
b2=7 m
b1=3 m
Area of trapezoid = (b1 +
b2) x h 2
A = (3m + 7m) x 8m
2
A = 10 m x
8 m 2
A = 80 m²
2
A = 40
m²
12. Let us find the area of this
trapezoid.
A = ½ (b1 + b2) x h
= ½ (5cm + 8cm) x
6cm
= ½ (13 cm x 6 cm)
= ½ (78 cm²)
= 39 cm²
13. 1.
12 cm
14 cm
20 cm
=1 cm
A= ½ (b1 + b2) x h or (b1 + b2) x h
2
A= ½ (12 cm + 20 cm) x 14 cm
A= ½ (32 cm) x 14 cm
A= ½ (448 cm²)
A= 224 cm²
A= ½ (b1 + b2) x h or (b1 + b2) x h
2
A= ½ (5 cm + 9cm) x 4cm
A= ½ (14 cm) x 4 cm
A= ½ (56 cm²)
A= 28 cm²
2.
14. Complete the table below by giving the base and height of each
trapezoid in cm, then find the corresponding area by using the
formula. Each square of the grid is 1 cm by 1 cm.
15. The area of a trapezoid is ½ of
the product of its two bases and
height.
A= (b1 + b2) x h
2
A= ½ (b1 + b2) x h
20. A. Multiple Choice. Choose the letter of the correct
answer.
4. The height of a trapezoid
is 9 cm. Its bases are 10 cm
and 12 cm. What is the area
of the trapezoid?
A.88 cm² C. 100 cm²
B.99 cm² D. 102 cm²
21. A. Multiple Choice. Choose the letter of the correct
answer.
5. What is the area of a
trapezoid whose bases are
13 m and 16 m, and whose
height is 4 m?
A.56 m² C. 60 m²
B. 58 m² D. 62 m²
22. B. Find the area of each trapezoid with the given
dimensions.
23. Consider the figure formed by two adjoining trapezoidal
residential lots. Find the area of each lot and the total area of
the two lots using the formula.
Lot 1: bases 18 m and 20 m ; h
= 16 m
Lot 2: bases 14 m and 15 m ; h
= 20 m
