RS Aggarwal Class 6 Math Thirteenth Chapter Angels And Their Measurement Exercise 13B Solution

RS Aggarwal Class 6 Math Thirteenth Chapter Angels And Their Measurement Exercise 13B Solution

EXERCISE 13B

Some Concepts About Angle

Magnitude Angle: The magnitude of an angle is amount of rotation through which one of the arms must be rotated about the vertex to bring it to the position of the other.

Right Angle: A quarter turn of a ray OA about O describes an angle called a right angle. 1 right angle = 90^o

VARIOUS TYPES OF ANGLES

Acute Angle: An angle whose measure is more than 0^o but less than 90^o is called acute angle.

Right Angle: An angle whose measure is 90^o is called right angle.

Obtuse Angle: An angle whose measure is more than 90^o but less than 180^o is called an obtuse angle.

Straight Angle: An angle whose measure is 180^o is called a straight angle.

Reflex Angle: An angle whose measure is more than 180^o but less than 360^o is called a reflex angle.

Complete Angle: An angle whose measure is 360^o is called a complete angle.

Zero Angle: The angle whose measure is 0^o is called a zero angle.

(1) State the type of each of the following angles:

Ans: (i) Obtuse angle

(ii) Right angle

(iii) Straight angle

(iv) Reflex angle

(v) acute angle

(vi) Complete angle

(2) Classify the angles whose magnitudes are given below:

(i) 30^o 

Ans: Acute

(ii) 91^o

Ans: Obtuse

(iii) 179^o

Ans: Obtuse

(iv) 90^o

Ans: Right

(v) 181^o

Ans: Reflex

(vi) 360^o

Ans: Complete

(vii) 128^o

Ans: Obtuse

(viii) (90.5)^o

Ans: Obtuse

(ix) (38.3)^o

Ans: Acute

(x) 80^o

Ans: Acute

(xi) 0^o

Ans: Zero

(xii) 15^o

Ans: Acute

(3) How many degrees are there in

(i) One right angle?

Ans: 90^o

(ii) Two right angles?

Ans: 180^o

(iii) Three right angles?

Ans: 270^o

(iv) Four right angles?

Ans: 360^o

(4) How many degrees are there in the angle between the hour hand and the minute hand of a clock, when it is

(i) 3 o’clock

Ans: 90^o                     

(ii) 6 o’clock

Ans: 180^o                                

(iii) 12 o’clock

Ans: 0^o                               

(iv) 9 o’clock

Ans: 90^o                      

(5) Using only a ruler, drawn an acute angle, an obtuse angle and a straight angle?

(i) ∠AOB is an acute angle.
(ii) ∠POQ is an obtuse angle.
(iii) ∠XOY = 180 degree = a straight angle.