Directions: Study the following questions carefully and choose the right answer.
1
An angle which is greater than 180° but less than 360° is called :
» Explain it
D
An angle which is greater than 180° but less than 360° is called a reflex angle.

Hence, option D is correct.

2
The complement of 72° 40’ is :
» Explain it
C
Complement of 72° 40’ is 90° ‒ (72° 40’)

= (89° 60’) ‒ (72° 40’) {since 1° = 60’}

= 17° 20’

Hence, option C is correct.


3
The supplement of 154° 30’ is :
» Explain it
A
Supplement of 154° 30’ is 180° ‒ (154° 30’)

= (179° 30’) ‒ (154° 30’) {since 1° = 60’}

= 25° 30’.

Hence, option A is correct.

4
Two straight lines AB and CD cut each other at O. If ∠BOD = 63°, then ∠BOC is :
» Explain it
B
As given ∠BOD = 63° 

Since COD is a straight line, we have :
 

 
∠BOC + ∠BOD = 180°. So, ∠BOC = (180° ‒ 63°) = 117°.

Hence, option B is correct.
 
5
The straight lines AD and BC intersect one another at the point O. If ∠AOB + ∠BOD + ∠DOC = 274°, then ∠AOC is :
» Explain it
A
As we know that the sum of all the angles around a point is 360°.
 

(∠AOB + ∠BOD + ∠DOC) + ∠AOC = 360°
 
∴ 274° + ∠AOC = 360° or ∠AOC = 86°.

Hence, option A is correct.