The document Geometry, For GMAT GMAT Notes | EduRev is a part of the GMAT Course Quantitative Aptitude for GMAT.

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**GEOMETRY **

**WHY you need to know Geometry:**

1. 4- 9 Geometry questions show up on the GMAT. 2. Geometry is based on a series of simple formulas. Knowing the formulas makes the questions easy to answer.

Note: If a Problem Solving question includes a drawing, then that drawing is usually to scale and can be used for estimation purposes (unless the question states that the ﬁgure is NOT drawn to scale). Note: If a Data Sufﬁciency question includes a drawing, then you should NOT TRUST IT. Some DS drawings are completely off; as such, they can not be used for estimation purposes. You can trust whatever numbers or descriptions you are given, but be suspicious of any picture that comes with a DS question.

**Lines**

Questions involving straight lines will likely include one or more of the following rules: 1. Lines add up to 180° 2. When lines criss-cross, opposite angles equal one another 3. Parallel lines, when crossed by a third line, will have the same set of 2 angles show up 4 times 4. Perpendicular lines form 90° angles at their meeting point

**Triangles**

Triangle questions will involve major rules and sometimes minor rules. Be on the lookout for each of these speciﬁc ideas on the GMAT: Major Rules:

**Major Rules:**

1. Triangles add up to 180°

2. Area =

3. Pythagorean Theorem:

4. Common Pythagorean triples:

• 3, 4, 5

• 5, 12, 13

5. Multiples of those triples for example:

• 9, 12, 15

• 50, 120, 130

6. 30°, 60°, 90° Triangle

7. 45°, 45°, 90° Triangle

Sometimes the following concepts show up; not every one will, but if they show, then you need to be ready for them.

**Minor Rules:**

1. Isosceles Triangles – 2 sides and 2 corresponding angles are equal

2. Equilateral Triangles – 3 sides are equal, all angles are 60 degrees

3. Hidden Right Triangles – in squares or equilateral triangles

4. Triangle Inequality Theorem – with 2 sides, you can ﬁgure out the minimum length of the third side (greater than the difference of the numbers) and the maximum (less than the sum of the numbers)

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