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RD Chapter 8- Lines and Angles Ex-8.1 Interview Questions Answers

Question 1 :

Write thecomplement of each of the following angles:

(i)200

(ii)350

(iii)900

(iv) 770

(v)300

Answer 1 :

(i) Thesum of an angle and its complement = 900

Therefore, the complement of 20= 900 –200 = 700

(ii) Thesum of an angle and its complement = 900

Therefore, the complement of 35° = 90° – 35° = 55

(iii) Thesum of an angle and its complement = 900

Therefore, the complement of 900 = 900 –900 = 00

(iv) Thesum of an angle and its complement = 900

Therefore, the complement of 770 = 90° – 770 = 130

(v) Thesum of an angle and its complement = 900

Therefore, the complement of 300 = 900 –300 = 600

Question 2 :

Write thesupplement of each of the following angles:

(i) 540

(ii) 1320

(iii) 1380

Answer 2 :

(i) Thesum of an angle and its supplement = 1800.

Therefore supplement of angle 540 = 1800 –540 = 1260

(ii) Thesum of an angle and its supplement = 1800.

Therefore supplement of angle 1320 = 1800 –1320 = 480

(iii) Thesum of an angle and its supplement = 1800.

Therefore supplement of angle 138= 180–1380 = 420

Question 3 :

If an angle is 280 lessthan its complement, find its measure?

Answer 3 :

Let the measure of any angle is ‘ a ‘ degrees

Thus, its complement will be (90 – a) 0

So, the required angle = Complement of a – 28

a = ( 90 – a ) – 28

2a = 62

a = 31

Hence, the angle measured is 310.

Question 4 :

If an angle is 30°more than one half of its complement, find the measure of the angle?

Answer 4 :

Let an angle measured by ‘ a ‘ in degrees

Thus, its complement will be (90 – a) 0

Required Angle = 300 +complement/2

a = 300 + (90 – a ) 0 / 2

a + a/2 = 300 + 450

3a/2 = 750

a = 500

Therefore, the measure of required angle is 500.

Question 5 :

Two supplementaryangles are in the ratio 4:5. Find the angles?

Answer 5 :

Two supplementary angles are in the ratio 4:5.

Let us say, the angles are 4a and 5a (in degrees)

Since angle are supplementary angles;

Which implies, 4a + 5a = 1800

9a = 1800

a = 200

Therefore, 4a = 4 (20) = 80and

5(a) = 5 (20) = 1000

Hence, required angles are 80° and 1000.

Question 6 :

Two supplementaryangles differ by 480. Find the angles?

Answer 6 :

Given: Two supplementary angles differ by 480.

Consider a0 beone angle then its supplementary angle will be equal to (180 – a) 0

According to the question;

(180 – a ) – x = 48

(180 – 48 ) = 2a

132 = 2a

132/2 = a

Or a = 660

Therefore, 180 – a = 1140

Hence, the two angles are 660 and1140.

Question 7 :

An angle is equalto 8 times its complement. Determine its measure?

Answer 7 :

Given: Required angle = 8 times of its complement

Consider a0 beone angle then its complementary angle will be equal to (90 – a) 0

According to the question;

a = 8 times of its complement

a = 8 ( 90 – a )

a = 720 – 8a

a + 8a = 720

9a = 720

a = 80

Therefore, the required angle is 800.


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RD Chapter 8- Lines and Angles Ex-8.1 Contributors

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