Mathematics
Write true (T) or false (F) :
(i) An angle whose measure is 90° is called a straight angle.
(ii) The sum of the angles of a linear pair is 180°.
(iii) When two straight lines cut each other, the sum of any two adjacent angles formed is 180°.
(iv) A line which intersects two other lines at their point of intersection is called a transversal.
(v) When two parallel lines are cut by a transversal, then the exterior opposite angles are supplementary.
Answer
(i) False
Reason — An angle of 90° is called a right angle. A straight angle measures exactly 180°.
(ii) True
Reason — By definition, a linear pair consists of adjacent angles formed by intersecting lines, which together form a straight line.
(iii) True
Reason — Any two adjacent angles formed by the intersection of two straight lines form a linear pair, making them supplementary.
(iv) False
Reason — A transversal is a line that intersects two or more lines at distinct (different) points. If it passes through their point of intersection, the lines are simply concurrent.
(v) False
Reason — When parallel lines are cut by a transversal, exterior alternate angles are equal, not supplementary. However, co-exterior angles (exterior angles on the same side of the transversal) are supplementary.
Related Questions
In the given figure, AB || CD. If ∠BNO = 128° and ∠COM = 56°, then ∠MON is
- 52°
- 64°
- 72°
- 84°
Fill in the blanks :
(i) An angle whose measure is more than 180° but less than 360° is called a …………… .
(ii) A straight line that intersects two or more lines in a plane is called a …………… .
(iii) A pair of adjacent angles is said to be a …………… if these angles have one arm common and other arms as opposite rays.
(iv) Two intersecting lines make …………… pairs of vertically opposite angles.
(v) Two lines are said to be …………… to each other if they intersect at right angles.
Mohit has a complex collection of lines drawn in a plane. He studies the angles formed due to the intersection of these lines. It is known that ∠DOH = 90°.
(1) Which of the following is a pair of vertically opposite angles ?
- ∠AOC, ∠BOG
- ∠BOG, ∠BOD
- ∠COE, ∠FOH
- ∠EOG, ∠FOH
(2) Which of the following is a pair of perpendicular lines ?
- AB, CD
- CD, GH
- AB, EF
- EF, GH
(3) Which of the following is a pair of complementary angles ?
- ∠AOC, ∠COE
- ∠COE, ∠EOG
- ∠EOG, ∠FOH
- ∠COG, ∠DOH
(4) Which of the following is a pair of supplementary angles ?
- ∠COE, ∠DOF
- ∠BOF, ∠AOH
- ∠AOE, ∠BOE
- ∠AOD, ∠BOG
Assertion: Two angles making a linear pair are always supplementary.
Reason: A pair of adjacent angles is said to be a linear pair, if these angles have one arm common and other arms as opposite rays.
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of Assertion (A).
- Assertion (A) is true but Reason (R) is false.
- Assertion (A) is false but Reason (R) is true.