The formula for calculating the area of a trapezoid is (b1 + b2)h/2, where b1 and b2 are the two parallel bases and h is the height or perpendicular distance between the bases. Several examples are given applying this formula to find the areas of different trapezoids where the dimensions are provided. The areas of two trapezoids are added together for problems 4 and 5.

1. Area of
trapezoids
(b1 + b2 )h
A=
2

2. Why?

3. Trapezoids:
Bases: are the two
sides that are parallel
base
height: is measurement
of the line that is
perpendicular (forms a ht
ht
90 angle) to one of the
0
bases. base

4. #1 22
cms
14
(b1 + b2 )h cms 8
A= cms
2 34
cms
( 22 + 34 ) 8 ( 56 ) 8
A= =
2 2
448
A=
2 A = 224 cms 2

5. #2 6.5 km
14
(b1 + b2 )h cms 11 km
A=
2 12.5 km
( 6.5 + 12.5 )11 ( 19 ) 11
A= =
2 2
209
A=
2 A = 104.5 km 2

6. #3 18
cms
8
(b1 + b2 )h cms 6
A= cms
2 30
cms
( 18 + 30 ) 6 ( 48 ) 6
A= =
2 2
288
A=
2 A = 144 cms 2

7. Base lines
#4 Trapezoid Are
Trapezoid #2
#1 Parallel
(b1 + b2 )h
A= 28
2 16 height is
5
Perpendicular
to base
19 11
( 5 + 28 ) 19 ( 28 + 16 ) 11
A= A=
2 2
313.5
( 33 ) 19 ( 44 ) 11
A= +242 A=
2 2
555.5
627 484
A= Add both
A=
2 Areas
2
Together!
A = 313.5 A = 242

8. Base lines
#5 Trapezoid Are
Trapezoid #2
#1 Parallel
(b1 + b2 )h
A= 24
2 13 height is
7 Perpendicular
to base
15 10
( 7 + 24 ) 15 ( 24 + 13 ) 10
A= A=
2 2
232.5
( 31 ) 15 ( 37 ) 10
A= +185 A=
2 417.5 2
465 370
A= Add both
A=
2 Areas
2
Together!
A = 232.5 A = 185