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Byju's Answer
Standard VIII
Mathematics
Area of a Triangle
Find the area...
Question
Find the area of pentagon
A
B
C
D
E
in which
B
L
⊥
A
C
,
C
M
⊥
A
D
and
E
N
⊥
A
D
such that
A
C
=
10
c
m
,
A
D
=
12
c
m
,
B
L
=
3
c
m
,
C
M
=
7
c
m
and
E
N
=
5
c
m
.
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Solution
Area of pentagon ABCDE= Area of
Δ
A
B
C
+
Area of
Δ
A
C
D
+
Area of
Δ
A
D
E
Here ,
B
L
⊥
A
C
,
C
M
⊥
A
D
,
E
N
⊥
A
D
So, BL,AM and EN perpendiculars to
Δ
A
B
C
,
Δ
A
C
D
Δ
A
D
E
respectively.
Area of triangle with perpendicular
=
1
2
×
b
a
s
e
×
h
e
i
g
h
t
∴
A
r
e
a
o
f
Δ
A
B
C
=
1
/
2
×
A
C
×
B
L
A
r
e
a
o
f
Δ
A
C
D
=
1
/
2
×
A
D
×
C
M
A
r
e
a
o
f
Δ
A
D
E
=
1
/
2
×
A
D
×
E
N
Now area of pentagon
A
B
C
D
E
=
1
/
2
A
C
×
B
L
+
1
/
2
×
A
D
×
C
M
+
1
/
2
×
A
D
×
E
N
=
(
1
/
2
×
10
×
3
)
+
(
1
/
2
×
12
×
7
)
+
(
1
/
2
×
12
×
5
)
=
15
+
42
+
30
=
87
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Similar questions
Q.
Find the area of pentagon ABCDE in which BL ⊥ AC, CM ⊥ AD and EN ⊥ AD such that AC = 10 cm, AD = 12 cm, BL = 3 cm, CM = 7 cm and EN = 5 cm.