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RRB Group D Angles & Lines

Study Material — 1 PYQs (2019–2019) · Concept Notes · Shortcuts

RRB Group D Angles & Lines is a frequently tested subtopic — 1 previous year questions from 2019–2019 papers are included below with concept notes, key rules and shortcut tricks.

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2019–2019
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8 Key Points
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Previous Year Questions

RRB Group D Angles & Lines — Past Exam Questions

1 questions from actual RRB Group D papers · all shown free · click option to reveal solution

Exam Q 12019Previous Year Pattern

Two straight lines AB and CD intersect at point O. If ∠AOC = 4x + 10° and ∠BOD = 3x + 30°, find the value of x.

Concept Notes

Angles & Lines— Rules & Concept

Core ConceptRead this first — the foundation of the topic
Key angle types include

Acute angles (less than 90°), Right angles (exactly 90°), Obtuse angles (90° to 180°), Straight angles (180°), Reflex angles (180° to 360°), and Complete angles (360°). Adjacent angles share a common vertex and side. Complementary angles add up to 90°. Supplementary angles add up to 180°. When parallel lines are cut by a transversal, several angle pairs are formed.

Corresponding angles are equal. Alternate interior angles are equal. Alternate exterior angles are equal. Co-interior angles are supplementary (add to 180°).

These properties solve most line-angle problems in SSC. Vertically opposite angles are always equal when two lines intersect. Linear pairs always add to 180°. When multiple angles meet at a point, they sum to 360°

Formulas to remember

Sum of interior angles of n-sided polygon = (n-2) × 180°. Each interior angle of regular polygon = (n-2) × 180° ÷ n. Each exterior angle of regular polygon = 360° ÷ n

SSC typically asks

Find missing angles using given relationships. Identify angle types in geometric figures. Calculate angles in polygons. Solve problems involving parallel lines and transversals.

Questions often combine angle properties with triangle or quadrilateral concepts.

ShortcutsUse these to save 30–60 seconds per question

For parallel line problems, remember CAIA rule - Corresponding, Alternate Interior, Alternate Exterior angles are Always equal. Co-interior angles Always add to 180°. This eliminates confusion during exams.

Worked ExampleSolve this step-by-step before moving on
1
Step 1

Co-interior angles are supplementary (add to 180°)

2
Step 2

Let the co-interior angle be x

3
Step 3

65° + x = 180°

4
Step 4

x = 180° - 65° = 115° Answer: 115° Another Shortcut: When solving polygon angle problems, use the quick formula: Interior angle = 180° - (360° ÷ n). This saves calculation time.

Exam TrapsCommon mistakes students make — avoid these

Students often confuse corresponding angles with co-interior angles. Remember - corresponding angles are EQUAL, co-interior angles are SUPPLEMENTARY. Also, many forget that exterior angles of any polygon always sum to 360°, regardless of the number of sides. Practice identifying angle relationships quickly.

Most SSC questions test basic properties rather than complex proofs. Focus on recognizing patterns and applying formulas accurately.

Key Points to Remember

  • Complementary angles add to 90°, supplementary angles add to 180°
  • Vertically opposite angles are always equal when two lines intersect
  • Corresponding and alternate angles are equal when parallel lines are cut by transversal
  • Co-interior angles are supplementary (add to 180°) in parallel line systems
  • Linear pair of angles always sums to 180°
  • Sum of interior angles of n-sided polygon = (n-2) × 180°
  • Each exterior angle of regular polygon = 360° ÷ n
  • All angles around a point sum to 360°

Exam-Specific Tips

  • Sum of all exterior angles of any polygon is always 360°
  • Each interior angle of regular hexagon is 120°
  • Each interior angle of regular octagon is 135°
  • Straight angle measures exactly 180°
  • Complete angle measures exactly 360°
  • Sum of interior angles of triangle is 180°
  • Sum of interior angles of quadrilateral is 360°
  • Each interior angle of square is 90°
Practice MCQs

Angles & Lines — Practice Questions

3graded MCQs · easy to hard · full solution & trap analysis

All MCQs →
Practice 1easy

Two lines intersect each other. One of the angles formed is 65°. What is the measure of the angle adjacent to it on a straight line?

Practice 2medium

Two lines intersect such that one of the angles formed is 65°. A third line is drawn parallel to one of the intersecting lines. If this third line intersects the second of the original two lines, what is the measure of the acute angle formed between the third line and the second line?

Practice 3hard

Two straight lines intersect at point O. A third line passes through O and makes an angle of 35° with the first line. If the angle between the second and third lines is 62°, what is the angle between the first and second lines?

60-Second Revision — Angles & Lines

  • Remember: CAIA rule for parallel lines - Corresponding, Alternate angles Equal, Co-interior Supplementary
  • Formula: Interior angles sum = (n-2) × 180° for n-sided polygon
  • Trap: Don't confuse corresponding angles (equal) with co-interior angles (supplementary)
  • Quick check: Exterior angles of any polygon always sum to 360°
  • Remember: Vertically opposite angles are always equal
  • Formula: Each exterior angle of regular polygon = 360° ÷ n
  • Key: Linear pairs and supplementary angles both add to 180°
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