# NCERT solutions for Mathematics Exemplar Class 11 chapter 7 - Permutations and Combinations [Latest edition]

## Chapter 7: Permutations and Combinations

Solved ExamplesExercise
Solved Examples [Pages 115 - 121]

### NCERT solutions for Mathematics Exemplar Class 11 Chapter 7 Permutations and Combinations Solved Examples [Pages 115 - 121]

Solved Examples | Q 1 | Page 115

In a class, there are 27 boys and 14 girls. The teacher wants to select 1 boy and 1 girl to represent the class for a function. In how many ways can the teacher make this selection?

Solved Examples | Q 2.(i) | Page 116

How many numbers are there between 99 and 1000 having 7 in the units place?

Solved Examples | Q 2.(ii) | Page 116

How many numbers are there between 99 and 1000 having atleast one of their digits 7?

Solved Examples | Q 3 | Page 116

In how many ways can this diagram be coloured subject to the following two conditions?
(i) Each of the smaller triangle is to be painted with one of three colours: red, blue or green.
(ii) No two adjacent regions have the same colour.

Solved Examples | Q 4.(i) | Page 117

In how many ways can 5 children be arranged in a line such that two particular children of them are always together

Solved Examples | Q 4.(ii) | Page 117

In how many ways can 5 children be arranged in a line such that two particular children of them are never together.

Solved Examples | Q 5 | Page 117

If all permutations of the letters of the word AGAIN are arranged in the order as in a dictionary. What is the 49th word?

Solved Examples | Q 6 | Page 117

In how many ways 3 mathematics books, 4 history books, 3 chemistry books and 2 biology books can be arranged on a shelf so that all books of the same subjects are together.

Solved Examples | Q 7 | Page 117

A student has to answer 10 questions, choosing atleast 4 from each of Parts A and B. If there are 6 questions in Part A and 7 in Part B, in how many ways can the student choose 10 questions?

Solved Examples | Q 8 | Page 118

Suppose m men and n women are to be seated in a row so that no two women sit together. If m > n, show that the number of ways in which they can be seated is (m!(m + 1)!)/((m - n + 1)1)

Solved Examples | Q 9 | Page 118

Three married couples are to be seated in a row having six seats in a cinema hall. If spouses are to be seated next to each other, in how many ways can they be seated? Find also the number of ways of their seating if all the ladies sit together.

Solved Examples | Q 10 | Page 119

In a small village, there are 87 families, of which 52 families have atmost 2 children. In a rural development programme 20 families are to be chosen for assistance, of which atleast 18 families must have at most 2 children. In how many ways can the choice be made?

Solved Examples | Q 11 | Page 119

A boy has 3 library tickets and 8 books of his interest in the library. Of these 8, he does not want to borrow Mathematics Part II, unless Mathematics Part I is also borrowed. In how many ways can he choose the three books to be borrowed?

Solved Examples | Q 12 | Page 119

Find the number of permutations of n different things taken r at a time such that two specific things occur together.

#### Objective Type Questions

Solved Examples | Q 13 | Page 120

There are four bus routes between A and B; and three bus routes between B and C. A man can travel round-trip in number of ways by bus from A to C via B. If he does not want to use a bus route more than once, in how many ways can he make round trip?

• 72

• 144

• 14

• 19

Solved Examples | Q 14 | Page 120

In how many ways a committee consisting of 3 men and 2 women, can be chosen from 7 men and 5 women?

• 45

• 350

• 4200

• 230

Solved Examples | Q 15 | Page 120

All the letters of the word ‘EAMCOT’ are arranged in different possible ways. The number of such arrangements in which no two vowels are adjacent to each other is ______.

• 360

• 144

• 72

• 54

Solved Examples | Q 16 | Page 120

Ten different letters of alphabet are given. Words with five letters are formed from these given letters. Then the number of words which have atleast one letter repeated is ______.

• 69760

• 30240

• 99748

• 99784

Solved Examples | Q 17 | Page 121

The number of signals that can be sent by 6 flags of different colours taking one or more at a time is ______.

• 63

• 1956

• 720

• 21

Solved Examples | Q 18 | Page 121

In an examination there are three multiple choice questions and each question has 4 choices. Number of ways in which a student can fail to get all answer correct is ______.

• 11

• 12

• 27

• 63

Solved Examples | Q 19 | Page 121

The straight lines l1, l2 and l3 are parallel and lie in the same plane. A total numbers of m points are taken on l1; n points on l2, k points on l3. The maximum number of triangles formed with vertices at these points are ______.

• ""^((m + n + k))"C"_3

• ""^((m + n + k))"C"_3 - ""^n"C"_3 - ""^6"C"_3 - ""^k"C"_3

• mC3 + nC3 + kC3

• mC3 × nC3 × kC3

Exercise [Pages 26 - 128]

### NCERT solutions for Mathematics Exemplar Class 11 Chapter 7 Permutations and Combinations Exercise [Pages 26 - 128]

Exercise | Q 1 | Page 122

Eight chairs are numbered 1 to 8. Two women and 3 men wish to occupy one chair each. First the women choose the chairs from amongst the chairs 1 to 4 and then men select from the remaining chairs. Find the total number of possible arrangements.

Exercise | Q 2 | Page 122

If the letters of the word RACHIT are arranged in all possible ways as listed in dictionary. Then what is the rank of the word RACHIT?

Exercise | Q 3 | Page 122

A candidate is required to answer 7 questions out of 12 questions, which are divided into two groups, each containing 6 questions. He is not permitted to attempt more than 5 questions from either group. Find the number of different ways of doing question

Exercise | Q 4 | Page 122

Out of 18 points in a plane, no three are in the same line except five points which are collinear. Find the number of lines that can be formed joining the point

Exercise | Q 5 | Page 122

We wish to select 6 persons from 8, but if the person A is chosen, then B must be chosen. In how many ways can selections be made?

Exercise | Q 6 | Page 122

How many committee of five persons with a chairperson can be selected from 12 persons.

Exercise | Q 7 | Page 122

How many automobile license plates can be made if each plate contains two different letters followed by three different digits?

Exercise | Q 8 | Page 122

A bag contains 5 black and 6 red balls. Determine the number of ways in which 2 black and 3 red balls can be selected from the lot.

Exercise | Q 9 | Page 122

Find the number of permutations of n distinct things taken r together, in which 3 particular things must occur together.

Exercise | Q 10 | Page 122

Find the number of different words that can be formed from the letters of the word ‘TRIANGLE’ so that no vowels are together

Exercise | Q 11 | Page 122

Find the number of positive integers greater than 6000 and less than 7000 which are divisible by 5, provided that no digit is to be repeated.

Exercise | Q 12 | Page 123

There are 10 persons named P1, P2, P3, ... P10. Out of 10 persons, 5 persons are to be arranged in a line such that in each arrangement P1 must occur whereas P4 and P5 do not occur. Find the number of such possible arrangements.

Exercise | Q 13 | Page 123

There are 10 lamps in a hall. Each one of them can be switched on independently. Find the number of ways in which the hall can be illuminated.

Exercise | Q 14 | Page 123

A box contains two white, three black and four red balls. In how many ways can three balls be drawn from the box, if atleast one black ball is to be included in the draw

Exercise | Q 15 | Page 123

If nCr – 1 = 36, nCr = 84 and nCr + 1 = 126, then find rC2.

Exercise | Q 16 | Page 123

Find the number of integers greater than 7000 that can be formed with the digits 3, 5, 7, 8 and 9 where no digits are repeated.

Exercise | Q 17 | Page 123

If 20 lines are drawn in a plane such that no two of them are parallel and no three are concurrent, in how many points will they intersect each other?

Exercise | Q 18 | Page 123

In a certain city, all telephone numbers have six digits, the first two digits always being 41 or 42 or 46 or 62 or 64. How many telephone numbers have all six digits distinct?

Exercise | Q 19 | Page 123

In an examination, a student has to answer 4 questions out of 5 questions; questions 1 and 2 are however compulsory. Determine the number of ways in which the student can make the choice.

Exercise | Q 20 | Page 123

A convex polygon has 44 diagonals. Find the number of its sides.

Exercise | Q 21 | Page 123

18 mice were placed in two experimental groups and one control group, with all groups equally large. In how many ways can the mice be placed into three groups?

Exercise | Q 22.(i) | Page 123

A bag contains six white marbles and five red marbles. Find the number of ways in which four marbles can be drawn from the bag if they can be of any colour

Exercise | Q 22.(ii) | Page 123

A bag contains six white marbles and five red marbles. Find the number of ways in which four marbles can be drawn from the bag if two must be white and two red

Exercise | Q 22.(iii) | Page 123

A bag contains six white marbles and five red marbles. Find the number of ways in which four marbles can be drawn from the bag if they must all be of the same colour.

Exercise | Q 23.(i) | Page 124

In how many ways can a football team of 11 players be selected from 16 players? How many of them will include 2 particular players?

Exercise | Q 23.(ii) | Page 124

In how many ways can a football team of 11 players be selected from 16 players? How many of them will exclude 2 particular players?

Exercise | Q 24 | Page 124

A sports team of 11 students is to be constituted, choosing at least 5 from Class XI and atleast 5 from Class XII. If there are 20 students in each of these classes, in how many ways can the team be constituted?

Exercise | Q 25.(i) | Page 124

A group consists of 4 girls and 7 boys. In how many ways can a team of 5 members be selected if the team has no girls

Exercise | Q 25.(ii) | Page 124

A group consists of 4 girls and 7 boys. In how many ways can a team of 5 members be selected if the team has at least one boy and one girl

Exercise | Q 25.(iii) | Page 124

A group consists of 4 girls and 7 boys. In how many ways can a team of 5 members be selected if the team has at least three girls.

#### Objective Type Questions from 26 to 40

Exercise | Q 26 | Page 124

If nC12 = nC8, then n is equal to ______.

• 20

• 12

• 6

• 30

Exercise | Q 27 | Page 124

The number of possible outcomes when a coin is tossed 6 times is ______.

• 36

• 64

• 12

• 32

Exercise | Q 28 | Page 124

The number of different four-digit numbers that can be formed with the digits 2, 3, 4, 7 and using each digit only once is ______.

• 120

• 96

• 24

• 100

Exercise | Q 29 | Page 124

The sum of the digits in unit place of all the numbers formed with the help of 3, 4, 5 and 6 taken all at a time is ______.

• 432

• 108

• 36

• 18

Exercise | Q 30 | Page 124

Total number of words formed by 2 vowels and 3 consonants taken from 4 vowels and 5 consonants is equal to ______.

• 60

• 120

• 7200

• 720

Exercise | Q 31 | Page 124

A five-digit number divisible by 3 is to be formed using the numbers 0, 1, 2, 3, 4 and 5 without repetitions. The total number of ways this can be done is ______.

• 216

• 600

• 240

• 3125

Exercise | Q 32 | Page 125

Everybody in a room shakes hands with everybody else. The total number of handshakes is 66. The total number of persons in the room is ______.

• 11

• 12

• 13

• 14

Exercise | Q 33 | Page 125

The number of triangles that are formed by choosing the vertices from a set of 12 points, seven of which lie on the same line is ______.

• 105

• 15

• 175

• 185

Exercise | Q 34 | Page 125

The number of parallelograms that can be formed from a set of four parallel lines intersecting another set of three parallel lines is ______.

• 6

• 18

• 12

• 9

Exercise | Q 35 | Page 125

The number of ways in which a team of eleven players can be selected from 22 players always including 2 of them and excluding 4 of them is ______.

• 16C11

• 16C5

• 16C9

• 20C9

Exercise | Q 36 | Page 125

The number of 5-digit telephone numbers having atleast one of their digits repeated is ______.

• 90,000

• 10,000

• 30,240

• 69,760

Exercise | Q 37 | Page 125

The number of ways in which we can choose a committee from four men and six women so that the committee includes at least two men and exactly twice as many women as men is ______.

• 94

• 126

• 128

• None

Exercise | Q 38 | Page 125

The total number of 9 digit numbers which have all different digits is ______.

• 10!

• 9!

• 9 × 9!

• 10 × 10!

Exercise | Q 39 | Page 125

The number of words which can be formed out of the letters of the word ARTICLE, so that vowels occupy the even place is ______.

• 1440

• 144

• 7!

• 4C4 × 3C3

Exercise | Q 40 | Page 125

Given 5 different green dyes, four different blue dyes and three different red dyes, the number of combinations of dyes which can be chosen taking at least one green and one blue dye is ______.

• 3600

• 3720

• 3800

• 3600

#### Fill in the Blanks 41 to 50

Exercise | Q 41 | Page 125

If nPr = 840, nCr = 35, then r = ______.

Exercise | Q 42 | Page 125

15C8 + 15C915C615C7 = ______.

Exercise | Q 43 | Page 125

The number of permutations of n different objects, taken r at a line, when repetitions are allowed, is ______.

Exercise | Q 44 | Page 126

The number of different words that can be formed from the letters of the word INTERMEDIATE such that two vowels never come together is ______.

Exercise | Q 45 | Page 126

Three balls are drawn from a bag containing 5 red, 4 white and 3 black balls. The number of ways in which this can be done if at least 2 are red is ______.

Exercise | Q 46 | Page 126

The number of six-digit numbers, all digits of which are odd is ______.

Exercise | Q 47 | Page 126

In a football championship, 153 matches were played, Every two teams played one match with each other. The number of teams, participating in the championship is ______.

Exercise | Q 48 | Page 126

The total number of ways in which six ‘+’ and four ‘–’ signs can be arranged in a line such that no two signs ‘–’ occur together is ______.

Exercise | Q 49 | Page 126

A committee of 6 is to be chosen from 10 men and 7 women so as to contain atleast 3 men and 2 women. In how many different ways can this be done if two particular women refuse to serve on the same committee ______.

Exercise | Q 50 | Page 26

A box contains 2 white balls, 3 black balls and 4 red balls. The number of ways three balls be drawn from the box if at least one black ball is to be included in the draw is ______.

#### State whether the following statement is True or False: 51 to 59

Exercise | Q 51 | Page 126

There are 12 points in a plane of which 5 points are collinear, then the number of lines obtained by joining these points in pairs is 12C25C2.

• True

• False

Exercise | Q 52 | Page 126

Three letters can be posted in five letterboxes in 35 ways.

• True

• False

Exercise | Q 53 | Page 126

In the permutations of n things, r taken together, the number of permutations in which m particular things occur together is ""^(n - m)"P"_(r - m) xx ""^r"P"_m.

• True

• False

Exercise | Q 54 | Page 126

In a steamer there are stalls for 12 animals, and there are horses, cows and calves (not less than 12 each) ready to be shipped. They can be loaded in 312 ways.

• True

• False

Exercise | Q 55 | Page 126

If some or all of n objects are taken at a time, the number of combinations is 2n – 1.

• True

• False

Exercise | Q 56 | Page 127

There will be only 24 selections containing at least one red ball out of a bag containing 4 red and 5 black balls. It is being given that the balls of the same colour are identical.

• True

• False

Exercise | Q 57 | Page 127

Eighteen guests are to be seated, half on each side of a long table. Four particular guests desire to sit on one particular side and three others on other side of the table. The number of ways in which the seating arrangements can be made is (11!)/(5!6!) (9!)(9!).

• True

• False

Exercise | Q 58 | Page 127

A candidate is required to answer 7 questions out of 12 questions which are divided into two groups, each containing 6 questions. He is not permitted to attempt more than 5 questions from either group. He can choose the seven questions in 650 ways.

• True

• False

Exercise | Q 59 | Page 127

To fill 12 vacancies there are 25 candidates of which 5 are from scheduled castes. If 3 of the vacancies are reserved for scheduled caste candidates while the rest are open to all, the number of ways in which the selection can be made is 5C3 × 20C9.

• True

• False

#### Match the column C1 to C2 from 60 to 64:

Exercise | Q 60 | Page 127

There are 3 books on Mathematics, 4 on Physics and 5 on English. How many different collections can be made such that each collection consists of:

 C1 C2 (a) One book of each subject; (i) 3968 (b) At least one book of each subject: (ii) 60 (c) At least one book of English: (iii) 3255
Exercise | Q 61 | Page 127

Five boys and five girls form a line. Find the number of ways of making the seating arrangement under the following condition:

 C1 C2 (a) Boys and girls alternate: (i) 5! × 6! (b) No two girls sit together : (ii) 10! – 5! 6! (c) All the girls sit together (iii) (5!)2 + (5!)2 (d) All the girls are never together : (iv) 2! 5! 5!
Exercise | Q 62 | Page 128

There are 10 professors and 20 lecturers out of whom a committee of 2 professors and 3 lecturer is to be formed. Find:

 C1 C2 (a) In how many ways committee: can be formed (i) 10C2 × 19C3 (b) In how many ways a particular: professor is included (ii) 10C2 × 19C2 (c) In how many ways a particular: lecturer is included (iii) 9C1 × 20C3 (d) In how many ways a particular: lecturer is excluded (iv) 10C2 × 20C3
Exercise | Q 63 | Page 128

Using the digits 1, 2, 3, 4, 5, 6, 7, a number of 4 different digits is formed. Find

 C1 C2 (a) How many numbers are formed? (i) 840 (b) How many number are exactly divisible by 2? (i) 200 (c) How many numbers are exactly divisible by 25? (iii) 360 (d) How many of these are exactly divisible by 4? (iv) 40
Exercise | Q 64 | Page 128

How many words (with or without dictionary meaning) can be made from the letters of the word MONDAY, assuming that no letter is repeated, if

 C1 C2 (a) 4 letters are used at a time (i) 720 (b) All letters are used at a time (ii) 240 (c) All letters are used but the first is a vowel (iii) 360

## Chapter 7: Permutations and Combinations

Solved ExamplesExercise

## NCERT solutions for Mathematics Exemplar Class 11 chapter 7 - Permutations and Combinations

NCERT solutions for Mathematics Exemplar Class 11 chapter 7 (Permutations and Combinations) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Mathematics Exemplar Class 11 solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com provide such solutions so that students can prepare for written exams. NCERT textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Mathematics Exemplar Class 11 chapter 7 Permutations and Combinations are Combination, Permutations, Fundamental Principles of Counting, Introduction of Permutations and Combinations, Permutation Formula to Rescue and Type of Permutation, Smaller Set from Bigger Set, Derivation of Formulae and Their Connections, Simple Applications of Permutations and Combinations, Factorial N (N!) Permutations and Combinations.

Using NCERT Class 11 solutions Permutations and Combinations exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in NCERT Solutions are important questions that can be asked in the final exam. Maximum students of CBSE Class 11 prefer NCERT Textbook Solutions to score more in exam.

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