Geometry Properties for SSC CGL Exams Tier 1, Tier 2

Geometry Properties for SSC CGL Exams Tier 1, Tier 2

In SSC CGL Geometry is considered the most important topic. It contributes around 8-10 marks in Tier 1 math and 16-18 question in Tier 2. It means there is 15-20% role of geometry in SSC CGL math. Out of 8-10 questions 5-6 questions are directly related to properties.

I will cover the geometry portion in 5 articles.

Article 1: Current article: properties of Lines, Angle,Triangle

Article 2: Properties of Quadrilateral , Polygon

Articles 3: Properties of Circle, Concept of Triplet, special points to be noted on geometry

Article 4: 20 Most important Questions on Geometry for SSC CGL

Articles : 21-40 Most Important questions on Geometry for SSC CGL exams.

What does Geometry include?

• Lines
• Angles
• Triangle
• Quadrilateral
• Polygon
• Circle

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Let us discuss one by one and start with article 1 i.e. current article. 

Lines 

AB and CD are two parallel lines. EF is a transverse line .

• vertically opposite angles are equal e.g. ∠2 = ∠4
• ∠1 and ∠2 are called adjacent angles
• ∠1 = ∠5 are called corresponding angles
• ∠4 = ∠6 are called alternate angles
• ∠3 + ∠6 =180° are called interior angles. Useful to understand quadrilateral angles.
• In other words interior angles same side = 2 right angles = 180° = π radians = 1/2 turn
• Sum of exterior angles same side ∠2 + ∠7 = 180°

Angle Bisector 

Triangle two Types 

Based on sides 

• Equilateral Triangle : All three sides equal
• Isosceles Triangle : Two sides equal
• Scalene Triangle : all three sides different

Based on Angles

• Right Angle Triangle : One angle 90°
• Obtuse Angle Triangle : One angle more than 90°
• Acute Angle Triangle : All angles less than 90°

Congruence of triangles

What is congruence?

When a triangle exactly covers other triangle i.e. mirror image

Triangle are always congruence when

• SSS : When three sides are equal
• ASA : When two angles and one side equal
• SAS : When two sides and one angle  equal.

Then what is similar triangle: 

In case of similarity

Median 

• Each median is split into 1:2
• Meet at a point G = Centroid

If area of triangle AGE is 24cm², then area of quadrilateral BDGF would be 48 cm^3. 

In fact median AD divides triangle in to equal parts. Also three triangle AGB, AGC, BGC are equal.

If we join EF then area of triangle GEF are alsways equal to 1/12 of triangle ABC.

Important points about triangle:

• Sum of two sides of a triangle are always greater than third side and difference of two sides of  a triangle is always smaller than third side.