Q11Written answer
In the following figure, is ∠1 adjacent to ∠2? Give reasons.
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Worked solution
Solution:-
∠1 and ∠2 are not adjacent angles because they are not lying on the same vertex.
NCERT · Class 7 · Maths
Chapter 5: Lines and Angles
Practice each question, then open the answer or worked solution.
Exercise 5.1
Textbook page 101 · 14 questionsQ12Written answer
Find the values of the angles x, y, and z in each of the following:
(i)
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Worked solution
Solution:-
∠x = 55o, because vertically opposite angles.
∠x + ∠y = 180o … [∵ linear pair]
= 55o + ∠y = 180o
= ∠y = 180o – 55o
= ∠y = 125o
Then, ∠y = ∠z … [∵ vertically opposite angles]
∴ ∠z = 125o
(ii)
Solution:-
∠z = 40o, because vertically opposite angles.
∠y + ∠z = 180o … [∵ linear pair]
= ∠y + 40o = 180o
= ∠y = 180o – 40o
= ∠y = 140o
Then, 40 + ∠x + 25 = 180o … [∵angles on straight line]
65 + ∠x = 180o
∠x = 180o – 65
∴ ∠x = 115o
Q13Written answer
Fill in the blanks.
(i) If two angles are complementary, then the sum of their measures is _______.
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Solution:-
If two angles are complementary, then the sum of their measures is 90o.
(ii) If two angles are supplementary, then the sum of their measures is ______.
Solution:-
If two angles are supplementary, then the sum of their measures is 180o.
(iii) Two angles forming a linear pair are _______________.
Solution:-
Two angles forming a linear pair are supplementary.
(iv) If two adjacent angles are supplementary, they form a ___________.
Solution:-
If two adjacent angles are supplementary, they form a linear pair.
(v) If two lines intersect at a point, then the vertically opposite angles are always
_____________.
Solution:-
If two lines intersect at a point, then the vertically opposite angles are always equal.
(vi) If two lines intersect at a point, and if one pair of vertically opposite angles are acute angles, then the other pair of vertically opposite angles are __________.
Solution:-
If two lines intersect at a point, and if one pair of vertically opposite angles are acute angles, then the other pair of vertically opposite angles are obtuse angles.
Q14Written answer
In the adjoining figure, name the following pairs of angles.
(i) Obtuse vertically opposite angles
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Worked solution
Solution:-
∠AOD and ∠BOC are obtuse vertically opposite angles in the given figure.
(ii) Adjacent complementary angles
Solution:-
∠EOA and ∠AOB are adjacent complementary angles in the given figure.
(iii) Equal supplementary angles
Solution:-
∠EOB and EOD are the equal supplementary angles in the given figure.
(iv) Unequal supplementary angles
Solution:-
∠EOA and ∠EOC are the unequal supplementary angles in the given figure.
(v) Adjacent angles that do not form a linear pair
Solution:-
∠AOB and ∠AOE, ∠AOE and ∠EOD, ∠EOD and ∠COD are the adjacent angles that do not form a linear pair in the given figure.