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1. Free GMAT Guide Introduction

2. GMAT General Strategies

3. Part 1: GMAT Essay Intro
3a. Analysis of an Argument
3b. Analysis of an Issue

4. Part 2: GMAT Verbal Intro
4a. Critical Reasoning
4b. Reading Comprehension
4c. Sentence Correction

5. Part 3: GMAT Math Intro

5a. Arithmetic
gmatNumber Rules
gmatLCM and HCF
gmatLinear Equations & Averages
gmatRatio & Variation
gmatTime, Speed & Distance

5b. Algebra
gmatAlgebraic Expressions
gmatQuadratic Equations
gmatPermutations
gmatProbability
gmatSequences & Series

5c. Geometry
gmatLines, Angles, & Geometry
gmatTriangles & Polygons
gmatCircles
gmatBasic Trigonometry

5d. Data Sufficiency
gmatData Sufficiency Introduction




  GMAT-MBA-Prep.com provides a free introductory course for the GMAT. This guide is designed to get your math and verbal skills up to speed so that you can make the most from a classroom or online GMAT course.  

5b3. Permutations
 

gmat
Permutations

A permutation is an ordered arrangement of every or some elements of a set of objects. Order is important in a permutation; therefore, permutations with the same objects in a different order are considered distinct arrangements.

For example if there are two objects A and B then the different arrangements are, AB and BA, thus there are two ways in which A and B can be arranged. A permutation of n distinct objects taken r at a time is a subset, with r elements, of the n distinct objects. If there are n distinct objects then the different possible arrangements taking r of them is denoted as:

 

Examples

1. Six flights are scheduled from city A to B and then back from B to A. In how many ways can a person go to B from A and then return to A if he doesn't takes the same flight for his return journey.

(A) 30               (B) 40               (C) 36              (D) 20              E) 24

Solution: The person can go from A to B in six ways. For the return journey he cannot take the same flight thus he can return in five ways. Therefore, the total number of ways = 6 × 5 = 30. Hence, (A)

2. In how many ways can a committee of 4 be formed out of 8 people?

(A) 140             (B) 60               (C) 70              (D) 72              (E) 42

Solution: The numbers of ways in which a committee of 4 can be selected out of 8 are:

Therefore: