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Byju's Answer
Standard IX
Mathematics
Triangle and Sum of Its Internal Angles
In A B C, if ...
Question
In
∆ABC, if ∠A − ∠B = 42° and ∠B − ∠C = 21°, ∠B = ?
(a) 95°
(b) 53°
(c) 32°
(d) 63°
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Solution
(b) 53°
Let
∠
A
-
∠
B
=
42
°
.
.
.
i
and
∠
B
-
∠
C
=
21
°
.
.
.
i
i
Adding
(
i
)
and
(
i
i
)
,
we get:
∠
A
-
∠
C
=
63
°
∠
B
=
∠
A
-
42
°
Using
i
∠
C
=
∠
A
-
63
°
Using
i
i
i
∴
∠
A
+
∠
B
+
∠
C
=
180
°
Sum of the angles of a triangle
⇒
∠
A
+
∠
A
-
42
°
+
∠
A
-
63
°
=
180
°
⇒
3
∠
A
-
105
°
=
180
°
⇒
3
∠
A
=
285
°
⇒
∠
A
=
95
°
∴
∠
B
=
95
-
42
°
⇒
∠
B
=
53
°
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Similar questions
Q.
In
a ∆ABC, if ∠A − ∠B = 42° and ∠B − ∠C = 21° then ∠B = ?
(a) 32°
(b) 63°
(c) 53°
(d) 95°
Figure
Q.
I
n
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Q.
If A - B - C and d(B,C) = 11, d(A,B) = 21, then d(A,C) = ________.
Q.
In Fig. 42, ABCD is a parallelogram in which AD = 21 cm, DH =18 cm and DK = 27 cm.
The length of AB is
(a) 63 cm (b) 63.5 cm (c) 31.5 cm (d) 31 cm