NCERT Class 7 Mathematics Ganita Prakash: Chapter 5 — Parallel and Intersecting Lines
This chapter, 'Across the Line,' from NCERT's Class 7 Mathematics (Ganita Prakash), explores the relationships between lines on a plane surface. It introduces the concept of intersecting lines, where two lines meet at a single point. The chapter details how intersecting lines form four angles and introduces the property that vertically opposite angles are equal (e.g., ∠a = ∠c and ∠b = ∠d). It also defines linear pairs as adjacent angles formed by intersecting lines that sum up to 180°. Students will learn to identify and analyze these angle relationships, a fundamental concept in geometry for CBSE curriculum.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 7 |
| Subject | Mathematics |
| Book | Ganita Prakash |
| Chapter | Chapter 5 — Parallel and Intersecting Lines |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 3 minutes |
| Word count | 507 |
Learning outcomes
- Understand the concept of intersecting lines on a plane surface.
- Identify and count the angles formed by two intersecting lines.
- Recognize and apply the property of vertically opposite angles.
- Define and use the concept of linear pairs to find angle measures.
Vocabulary
| Word | Meaning |
|---|---|
| Intersect | When a pair of lines meet each other at a point on a plane surface. |
| Plane surface | A flat surface, like a table top or a piece of paper. |
| Angles | The figure formed by two rays sharing a common endpoint. |
| Vertically opposite angles | Angles opposite to each other when two lines intersect; they are equal. |
| Linear pair | Adjacent angles formed by two intersecting lines that add up to 180°. |
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Practice questions
- What happens when two lines intersect on a plane surface? Answer: They meet at a point, forming four angles.
- If two lines intersect and form angles ∠a, ∠b, ∠c, and ∠d, which angles are vertically opposite? Answer: ∠a and ∠c are vertically opposite, and ∠b and ∠d are vertically opposite.
- What is the sum of angles in a linear pair? Answer: 180°
- If ∠a = 100° in Fig. 5.2, what are the measures of ∠b, ∠c, and ∠d? Answer: ∠b = 80°, ∠c = 100°, ∠d = 80°
Frequently asked questions
What is an intersecting line?
When a pair of lines meet each other at a point on a plane surface, they are called intersecting lines.
How many angles are formed when two lines intersect?
Four angles are formed when two lines intersect.
Are vertically opposite angles equal?
Yes, when two lines intersect, the vertically opposite angles formed are always equal.
What is a linear pair?
A linear pair consists of two adjacent angles formed by two intersecting lines, and their sum is always 180°.
Can two straight lines intersect at more than one point?
No, two distinct straight lines can intersect at most at one point.
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NCERT Class 7 Mathematics — Ganita Prakash — Chapter 5 — Parallel and Intersecting Lines. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.