Math, Area of Trapezoid

2. Trapezoid
It is a quadrilateral
with exactly one pair
of parallel sides.

3. Illustration

4. A= ½ (b1+b2)h

6. Trapezoid Area Theorem
The area of any
trapezoid is equal to
one-half the product of
the height and the sum
of the bases (b1+b2).

7. How to find the
bases?
b1= 2A/h –b2
b2= 2A/h –b1

8. How to find the
height?
h= 2A/b1+b2

9. Example:
Find the Area of trapezoid DPRS.
18 cm
Solution:
A= ½(b1+b2)h
=1/2 (18cm+30cm)(12cm)
=288cm² 30 cm
12 cm

10. Example:
• Find the height of the trapezoid if its area is
16cm², b1= 4cm and b2=2.4cm.
Solution:
h= 2A/b1+b2
= 2(16cm²)/ 4cm+2.4cm
=32cm²/6.2cm
=5cm

11. Example:
• The bases of a trapezoid are
2 and 4 times the height.
The area is 108cm². Find the
height and the bases of the
trapezoid.

12. Solution:
h= 2A/b1+b2
=2(108cm²)/ 2h+4h
=216cm²/ 6h
h(6h)= 216cm²
6h² = 216cm²
h² =36
h= 6

13. b1= 2h
= 2(6)
=12
b2= 4h
=4(6)
=24
Check:
A=1/2(b1+b2)h
108cm²= ½(12+24)6cm
108cm²= ½(36)6cm
108cm² = 216cm²/2
108cm² = 108cm²
 check 

14. 
Daisy Mae A. Valeroso