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SSC GD Constable Angles & Lines

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This page covers SSC GD Constable Angles & Lines with complete concept notes, 15 graded practice MCQs, key points and exam-specific tips. Free to study.

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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

15graded MCQs · easy to hard · full solution & trap analysis

All MCQs →
Practice 1easy

An exterior angle of a triangle is 110°. If the two non-adjacent interior angles are in the ratio 3:2, what is the measure of the larger non-adjacent interior angle?

Practice 2easy

If two angles form a linear pair and one angle is 28° more than the other, what is the measure of the larger angle?

Practice 3easy

Two lines intersect each other. If one of the angles formed is 65°, what is the measure of the angle adjacent to it on a straight line?

Practice 4easy

Two complementary angles are in the ratio 1:5. What is the measure of the smaller angle?

Practice 5easy

Three angles of a triangle are in the ratio 2:3:4. What is the measure of the largest angle?

Practice 6easy

A transversal crosses two parallel lines. If one of the alternate interior angles is 72°, what is the other alternate interior angle?

Practice 7medium

Two intersecting lines form four angles. If one angle is 4 times another angle, what is the measure of the smaller angle?

Practice 8medium

Two lines intersect such that one of the angles formed is 65°. What is the measure of the angle adjacent to it on a straight line?

Practice 9medium

Three lines meet at a point. If two of the angles formed on one side of a straight line are 85° and 50°, what is the measure of the third angle?

Practice 10medium

Two parallel lines are cut by a transversal. If one of the alternate interior angles is 72°, what is the sum of the two co-interior angles (also called consecutive interior angles) on the same side of the transversal?

Practice 11medium

In a triangle, one exterior angle measures 130°. If the two non-adjacent interior angles are in the ratio 3:2, what is the measure of the larger of these two angles?

Practice 12hard

A transversal cuts two parallel lines. The ratio of one interior angle on one side of the transversal to the interior angle on the same side at the other parallel line is 2:3. What is the measure of the larger interior angle?

Practice 13hard

Two parallel lines are cut by two different transversals. The first transversal makes an angle of 65° with the first parallel line. The second transversal makes an angle of 50° with the second parallel line. What is the acute angle between the two transversals?

Practice 14hard

A transversal intersects two lines (not necessarily parallel) such that the sum of the two interior angles on the same side is 200°. If the two lines were to be parallel, what would be the difference between the actual sum and the required sum of co-interior angles?

Practice 15hard

Two lines intersect at point O. A ray from O bisects one of the angles formed. Another ray from O bisects the angle adjacent to the first bisected angle. What is the angle between these two bisecting rays?

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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