NCERT Solutions for Class 7 Mathematics: Chapter 5 – Lines and Angles

Get NCERT Solutions for Class 7 Mathematics,  Chapter 5 – Lines and Angles. This chapter is one of the most important chapters of CBSE Class 7 Mathematics subject. Students of Class 7 are advised to prepare this chapter well as concepts given in this chapter are required to solve questions of other chapters.

NCERT Solutions for Class 7 Mathematics  Chapter 5 – Lines and Angles

1. Find the complement of each of the following angles:

The sum of the measures of complementary angles is 90°.

(i) One angle is 20°

So, Complement = 90° − 20° = 70°

(ii) One angle is 63°

So, Complement = 90° − 63° = 27°

(iii) One angle is 57°

So, complement = 90° − 57° = 33°

2. Find the supplement of each of the following angles:

Solutions:

The sum of the measures of the supplementary angles is always  180°.

(i) One angle is 105°

So the supplement = 180° − 105° = 75°

(ii) One angle is 87°

So the supplement = 180° − 87° = 93°

(iii) One angle is 154°

So the supplement =  180° − 154° = 26°

3. Identify which of the following pairs of angles are complementary and which are supplementary.

(i) 65°, 115°

(ii) 63°, 27°

(iii) 112°, 68°

(iv) 130°, 50°

(v) 45°, 45°

(vi) 80°, 10°

Solutions:

The sum of the measures of supplementary angles is 180° and that of complementary angles is 90°

(i) Given angles are 65°, 115°

Sum = 65° + 115° = 180°

So, the angles are supplementary angles.

(ii) Given angles are 63°, 27°

Sum = 63° + 27° = 90°

So, the angles are complementary angles.

(iii) Given angles are 112°, 68°

Sum =  112° + 68° = 180°

So, the angles are supplementary angles.

(iv) Given angles are 130°, 50°

Sum =  130° + 50° = 180°

So, the angles are supplementary angles.

(v) Given angles are 45°, 45°

Sum =  45° + 45° = 90°

So, the angles are complementary angles.

(vi) Given angles are 80°, 10°

Sum =  80° + 10° = 90°

So, the angles are complementary angles.

4. Find the angle which is equal to its complement.

Solutions:

Suppose the angle is x.

According to the question, the complement of this angle is also x.

We know that the sum of the measures of a complementary angle pair is 90°.

So, x + x = 90°

2x = 90°

x = 90°/2 = 45°

5. Find the angle which is equal to its supplement.

Solutions:

Let the angle be x.

Supplement of this angle is also x.

As, the sum of the measures of a supplementary angle pair is 180°.

So, x + x = 180°

⇒ 2x = 180°

⇒ x = 90°

Answers of the remaining questions will be available here shortly.