LEVEL I. 3. In how many ways 4 identical white balls and 6 identical black balls be arranged in a row so that no two white balls are together?

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1 LEVEL I 1. Three numbers are chosen from 1,, 3..., n. In how many ways can the numbers be chosen such that either maximum of these numbers is s or minimum of these numbers is r (r < s)?. Six candidates are called for interview to fill four posts in an office. Assuming that each candidate is fit for each post, determine the number of ways in which (i) First and second posts can be filled (ii) First three posts can be filled. 3. In how many ways 4 identical white balls and 6 identical black balls be arranged in a row so that no two white balls are together? 4. Find the sum of the digits in the unit place of all the number formed with the help of 3, 4, 5, 6 taken all at a time. 5. There are 1 balls, which are either white or black. Balls of the same colour are alike. Find the number of white balls, so that the number of arrangements of these balls in a row be maximum. 6. 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. 7. How many different words can be formed with the letters of the word ORDINATE so that (i) the vowels occupy odd places. (ii) the word begin with O. (iii) the word begin with O and end with E. 8. The result of 11 chess matches (as win, loose or draw) are to be forecast. Out of all possible forecasts, find how many will have 8 correct and 3 incorrect results boys and 4 girls sit in a straight line. Find the number of ways in which they can be seat if girls are together and the other are also together but separate from the first. 10. How many 7 digit numbers are there the sum of whose digits is even?

2 LEVEL II 1. Prove that the number of words that can be formed out of the letter a, b, c, d, e and f taken three together, each word containing at least one vowel atleast is 96.. A candidate is required to answer 7 out of 15 questions which are divided into three groups A, B and C each containing 4, 5 and 6 questions respectively. He is required to select at least questions from each group. In how many ways can he make up his choice? 3. Four digit numbers are to be formed by using the digits 0, 1,, 3, 4, 5. What is the number of such numbers if (i) repetition is not allowed (ii) repetition is allowed, (iii) at least one digit is repeated? 4. There are 1 balls of which 4 are red, 3 black and 5 white. In how many ways can the balls be arranged in a line so that no two white balls occupy consecutive positions, if balls of the same colour are (i) identical. (ii) different. 5. A tea party is arranged for m people about two sides of a long table with m-chairs on each side r-men wish to sit on one particular side and s on the other. In how many ways they can be seated. (r, s m). 6. Find the number of subsets containing elements of the set {1,, 3,...,100}, sum of whose elements is divisible by In a chess tournament, where the participants are to play one game with one another two players fell ill, having played only 3 games each. If the total number of games played in the tournament is equal to 84 then find the number of participants in the beginning. 8. In a certain examination of 6 papers each paper has 100 marks as maximum marks. Show that the number of ways in which a candidate can secure 40% marks in the whole examination is 1 45! 144! 43! ! 40! 139! 38!. 9. In an examination the maximum marks for each of the three papers are n and for the fourth paper is n. Prove that the number of ways in which a candidate can get 3n marks is 1 6 (n + 1) (5n + 10n + 6). 10. Find the number of ways in which p identical white balls, q identical black balls & r identical red balls can be put in n different bags, if one or more of the bags remain empty.

3 SET I 1. In a college examination, a candidate is required to answer 6 out of 10 questions which are divided into two sections each containing 5 questions. Further the candidate is not permitted to attempt more than 4 questions from either of the section. The number of ways in which he can make up a choice of 6 questions, is (A) 00 (B) (D) 50. The number of way of seven digit number of the form a 1 a a 3 a 4 a 5 a 6 a 7, ( a i 0 i 1,,...,7) be present in decimal system, such that a 1 a a 3 a 4 a 5 a 6 a 7, is (A) 80 (B) (D) Ramesh has 6 friends. In how many ways can be invite one or more of them at a dinner? (A) 61 (B) 6 63 (D) 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 answers correct is (A) 11 (B) 1 7 (D) The straight lines I 1, I, I 3 are parallel and lie in the same plane. A total number of m points are taken on I 1, n points on I, k points on I 3. The maximum number of triangles formed with vertices at these points are (A) m + n + k C 3 (B) m + n + k C 3 - m C 3 - n C 3 - k C 3 m C 3 + n C 3 + k C 3 6. There are 10 lamps in a hall. Each one of them can be switched on independently. The number of ways in which the hall can be illuminated is (A) 10 (B) (D) 10! 7. How many numbers between 5000 and can be formed using the digits 1,, 3, 4, 5, 6, 7, 8, 9 each digit appearing not more than once in each number? (A) 5 8 P (B) C ! P (D) 3 5 C 3 8. The total number of permutations of 4 letters that can be made out of the letters of the word EXAMINATION is (A) 454 (B) The total number of selections (taking at least one) of fruit which can be made from 3 bananas, 4 apples and oranges is

4 (A) 59 (B) A lady gives a dinner party to 5 guests to be selected from nine friends. The number of ways of forming the party of 5, given that two of the friends will not attend the party together is (A) 56 (B) The greatest possible number of points of intersection of 8 straight lines and 4 circles is (A) 3 (B) (D) The number of all the possible selections which a student can make for answering one or more questions out of eight given questions in a paper, when each question has an alternative is (A) 56 (B) If n identical dice are rolled at a time, then total number of out comes is 6 n 6 (A) 6 n (B) 6 n n 5 C5 14. A father with 8 children takes them 3 at a time to the Zoological Gardens, as often as he can without taking the same 3 children together more than once. The number of times each child ( and father )will go to the garden respectively (A) 56, 1 (B) 1, 56 11, The number of ways in which four letters can be selected from the word DEGREE is (A) 7 (B) 6 6! 3! 16. Number of ways in which Rs. 18 can be distributed amongst four persons such that no body receives less than Rs. 4 is (A) 4 (B) 4 4! 17. There are five different green dyes, four different blue dyes and three different red dyes. The total number of combinations of dyes that can be chosen taking at least one green and one blue dye is (A) 355 (B) There are n straight lines in a plane, no two of which are parallel, and no three pass through the same point. Their points of intersection are joined. Then the number of fresh lines thus obtained is

5 (A) n( n 1)( n ) 8 n ( n 1 )( n )( n 3 ) 8 (B) n ( n 1 )( n )( n 3 ) All possible two-factor products are formed from the numbers 1,,..., 100. The number of factors out of the total obtained which are multiple of 3 is (A) 11 (B) The number of ways of choosing a committee of 4 women and 5 men from 10 women and 9 men, if Mr. A refuses to serve on the committee if Ms. B is member of the committee, cannot exceed (A) 0580 (B) (D) 000

6 SET II 1. The number of signals that can be generated by using 6 different coloured flags, when any number of them may be hoisted at a time is (A) 1956 (B) (D) The number of ways of distributing 5 prizes to 4 boys is (when each boy is eligible for any number of prizes) (A) 56 (B) (D) Total number of regions in which n coplanar circles can divide the plane, it is known that each pair of circles intersect in two different points and no three of them have common point of intersection, is equal to (A) 1 ( n n ) (B) 1 ( n 3n ) 1 3 ( n n ) (D) (n - n + ) 4. Number of sub parts into which ' n ' straight lines (no two are parallel and no three are concurrent ) in a plane can divide it is : (A) n n n n 6 (B) n n 4 5. The total number of arrangements which can be made out of the letters of the word ALGEBRA without altering the relative position of vowels and consonants is (A) 4!. 3! (B) 4!3! (4!. 3!) 6. m parallel lines in a plane are intersected by a family of n parallel lines. The total number of parallelograms so formed is (A) m 1 n 1 4 nm m 1 n 1 (B) mn 4 nm m 1 n 1 (D) 4 7. There are 0 persons among whom two are brothers. The number of ways in which we can arrange them around a circle so that there is exactly one person between the two brothers, is (A) (18!) (B) 18! (18! 18!)

7 8. The number of five digit numbers in which digits decrease from left to right, is (A) 9 C 5 (B) 10 C 5 10 C 5 (D) 10 P 5 9. The number of ways in which one can post 5 letters in 7 letter boxes is (A) 5 7 (B) 7 P (D) The number of permutations of all the letters of the word MISSISSIPPI is (A) (B) A box contains 5 different red and 6 different white balls. In how many ways can 6 balls be selected so that there are at least two balls of each colour (A) 45 (B) The number of ways of arranging m positive and n (< m + 1) negative signs in a row so that no two negative signs are together, is (A) m + 1 P n m + 1 C n (B) n + 1 P m (D) n + 1 C m 13. The total number of ways of selecting six coins out of 0 one rupee coins, 10 fifty paise coins and 7 twenty five paise coins, is (A) 6 (B) There are m copies of each of n different books in a university library. The number of ways in which one or more than one book can be selected is (A) m n + 1 (B) (m + 1) n 1 (n + 1) n m (D) m 15. The number of 5 - digit numbers in which no two consecutive digits are identical is (A) (B) There are 1 balls numbered from 1 to 1. The number of ways in which they can be used to fill 8 places in a row so that the balls are with numbers in ascending or descending order, is equal to (A) 1 C 8 (B) 1 P 8 1 P 8 (D) 1 C n is selected from the set {1,, 3,...100} and the number n + 3 n + 5 n is formed. Total number of ways of selecting n so that the formed number is divisible by 4, is equal to (A) 50 (B)

8 18. For a game in which two partners oppose two other partners, 6 men are available. If every possible pair must play every other pair, the number of games played is (A) 15 (B) (D) Five persons including one lady are to deliver lectures to an audience. The organizer can arrange the presentation of their lectures, so that the lady is always in the middle, is (A) 5 P 5 ways (B) 4. 4 P 4 ways 4! ways (D) 5 C 4 ways 0. Let m denote the number of ways in which 4 different books are distributed among 10 persons, each receiving none or one only and let n denote the number of ways of distribution if the books are all alike. Then (A) m = 4n (B) n = 4m m = 4n

9 More than one correct SET III 1. On the normal chess board as shown, I 1 and I are two insects which starts moving towards each other. Each insect moving with the same constant speed. Insect I 1 can move only to the right or upward along the lines while the insect I can move only to the left or downward along the lines of the chess board. The total number of ways the two insects can meet at same point during their trip is (A) (B) (D) C (16, 8). Number of quadrilaterals which can be constructed by joining the vertices of a convex polygon of 0 sides if none of the side of the polygon is also the side of the quadrilateral is 15 (A) 17 C 4 15 C (B) C (D) Consider the expansion, (a + a + a a 1 3 p )n where n N and n p. The correct statement(s) is/are (A) Number of different terms in the expansion is, n + p 1 C n (B) Co-efficient of any term in which none of the variables a 1, a,..., a p occur more than once is ' n ' Co-efficient of any term in which none of the variables a 1, a,..., a p occur more than once (D) is n! Number of terms in which none of the variables a 1, a,..., a p occur more than once is p c n 4. In an examination of 9 papers, a candidate has to pass in more papers than the number of papers in which he fails, in order to be successful. The number of ways in which he can be unsuccessful is (A) 55 (B) (D) Identify the correct statement(s). (A) Number of naughts standing at the end of 15 is 30 (B) A telegraph has 10 arms and each arm is capable of 9 distinct positions excluding the position of rest. The number of signals that can be transmitted is Number of numbers greater than 4 lacs which can be formed by using only the digits 0,, (D), 4, 4 and 5 is 90 In a table tennis tournament, every player plays with every other player. If the number of games played is 5050 then the number of players in the tournament is 100 I 1 I W I Let us examine the operation of addition and substraction on the set of natural numbers. If we add two natural numbers, we use to get a natural number but in case of substraction of one natural number with other output need not to be a natural number. Hence operation + is a binary

10 operation on the set of natural numbers ( it is commutative also), but operation is not a binary operation on the set of natural number. Note that operation is a binary on the set of integers. In general let an operation * on a non-empty set S is defined. If a i * a S j a i, a j S, then it is said to be a binary operation and it is said to be commutative if a i * a = a j j * a i a i, a j S. Let S = {a 1, a,..., a n } 6. Total number of binary operation on S will be (A) n (B) n n 7. Total number of binary operation on S which are commutative is (A) n n (B) n n n n n n n n (D) n 8. Total number of binary operation on S such that a i * a j a i * a, k j k, is (A) n! n (B) (n!) n n! n (D) (n + 1)! 9. Let a 1, a, a 3,...a n be the distinct real numbers, then total number of binary operation on S such that a i * a j a i * a j + 1 i, j, is n n (A) n 1 (B) n n n n n W II. The number of ways in which certain distinct object can be divided into some non-numbered groups = Factorial of total number of object Product of factorial number of elements in each group product of factorial of number of groups having same number of elements (if any) And number of ways in which certain distinct object can be divided into some numbered groups (this is also known as distribution) = Number of grouping (as in the previous) factorial of number of persons in which object was suppose to be distributed factorial of number of person who got nothing (if any) Example : The number of ways in which 0 distinct object can be divided in 6 groups 3 having two elements each, two having three elements each and one having eight elements, is 0!!!! 3! 3! 8! 3!! Example : The number of ways in which 0 distinct objects can be distributed among 7 person so that 4 them got 5 each and 3 of them got nothing, is 0! 7! 5! 5! 5! 5! 4! 3! 10. The number of ways in which 10 digits can be divided in groups of 5 each is o f

11 (A) 10! 5! 5!! (B) 10! 5! 5! 10! 5! 5! 11. The number of ways in which 6 alphabets can be distributed among 3 persons so that of them got 9 each 6! (A) 3! 9! 8!! 6! (B) 3! 9! 9! 8!! 6! 9! 8!! 1. The number of ways in which n distinct object can be distributed among n persons so that exactly one of them got nothing n n n (A) C n! (B) n n! n! C C 13. The number of ways in which 1 balls be divided into groups of 5, 4 and 3 respectively is (A) 1! 5!4!3! (B) 1! 3!(5!4!3!) 1! 4!4!4! 14. The number of ways in which 1 different balls be divided between boys, one of them receives 5 and the other 7 balls, is (A) 1560 (B) W III. If we have n-balls and r distinct boxes then number of ways of putting or arranging all the balls inside the boxes is given by following table Balls are distinct Blank box Order inside the Number of ways or Identical Allowed box required Distinct No Yes n 1 C r 1. n! Distinct Yes Yes n + r 1 C r 1. n! Distinct No No n r n r n r C 1(r 1) C (r ) r n C 3(r 3)... Distinct Yes No r n Identical No No n 1 C r 1 Identical Yes No n + r 1 C r The number of ways in which 9 non-zero digits can be used to form 3 natural number x, y, z so that

12 each digit used exactly once (A) 8 C. 9! (B) 11 C. 9! In how many ways a person can post 10 letters in 3 letter box so that in each box at least one letter is post (A) (B) In how many ways 10 person can stand in 4 rows (A) 10 C 3. 10! (B) 9 C 3. 10! 13 C 3. 10! 18. The number of ways in which 7 identical balls can be put in three boxes x, y, z (A) 9 C (B) 10 C 1 C 19. Fill In The Blanks : (i) Number of proper divisors of 50 which are divisible by 10 is and the sum of these divisors is. (ii) The smallest positive integer n with 4 divisors (including 1 and n) is. (iii) (iv) Team A and B play in a tournament. The first team that wins two games in a row or wins a total o f four games is considered to win the tournament. The number of ways in which tournament can occur is. Number of ways 3 tickets can be selected from a set of 100 tickets numbered, 1,, 3..., 100 so that the number on them are in geometric progression is. (v) Number of different heptagons which can be formed by joining the vertices of a polygon having 16 sides, if none of the sides of the polygon is the side of the heptagon is. (vi) (vii) (viii) (ix) (x) Number of 9 digits numbers divisible by nine using the digits from 0 to 9 if each digit is used atmost once is K. 8!, then K has the value equal to. In maths paper there is a question on "Match the column" in which column A contains 6 entries and each entry of column A corresponds to exactly one of the 6 entries given in column B written randomly. marks are awarded for each correct matching and 1 mark is deducted from each incorrect matching. A student having no subjective knowledge decides to match all the 6 entries randomly. The number of ways in which he can answer, to get atleast 5 % marks in this question is. There are p intermediate railway stations on a route from one terminus to other. Number of ways in which a train can be stopped at 3 stations if no two stations are consecutive is. If N = p 1. ( p 1), where p 1 is a prime, then the sum of the divisors of N expressed in terms of N is equal to. The number of ways of arranging m white and n red counters in straight line so that each arrangement is symmetrical with respect to a central mark is.

13 (assume that all counters are alike except for the colour) 0. Match The Column : (i) There are 'm' men & 'n' monkeys (n > m). Then match the entries of column I and II. Column I Column II (a) Number of ways in which each man may (P) n m become the owner of one monkey is (Q) n P m (b) Number of ways in which every monkey (R) m n has a master, if a man may have any number (S) m n of monkeys is (ii) 5 balls are to be placed in 3 boxes. Each box can hold all the 5 balls. Number of ways in which the balls can be placed so that no box remains empty, if Column I Column II (a) balls are identical but boxes are different (P) (b) balls are different but boxes are identical (Q) 5 (c) balls as well as boxes are identical (R) 50 (d) balls as well as boxes are identical but boxes are kept in a row (S) 6

14 LEVEL I ANSWER 1. n r C + s 1 C (s r 1). (i) 6 P (ii) 6 P C or (i) 4! 4! (ii) 7! (iii) 6! LEVEL II (a) 300 (b) 1080 (c) (a) 1960 (b) ! 8! 3! C n + p 1 C p. n + q 1 C q. n + r 1 C r SET I m r s 5. C m r m! 1. A. D 3. C 4. D 5. B 6. B 7. A 8. A 9. A 10. C 11. D 1. B 13. C 14. B 15. A 16. D 17. C 18. C 19. C 0. A SET II 1. A. D 3. D 4. A 5. B 6. D 7. A 8. B 9. C 10. B 11. A 1. C 13. B 14. B 15. C 16. D 17. B 18. B 19. C 0. C SET III 1. ABCD. ABC 3. ACD 4. B 5. BC 6. A 7. B 8. C 9. C 10. B 11. A 1. C 13. A 14. B 15. A 16. B 17. C 18. A 19. (i) 17, 4760 (ii) 360 (iii) 14 (iv) 53 (v) 64 (vi) 17. 8! (vii) 56 ways (viii) p C 3 (ix) N (x) ( m n )! n! m! 0. (i) a-q, b-s (ii) a-s, b-q, c-p, d-s

PERMUTATIONS AND COMBINATIONS

8 PERMUTATIONS AND COMBINATIONS FUNDAMENTAL PRINCIPLE OF COUNTING Multiplication Principle : If an operation can be performed in 'm' different ways; following which a second operation can be performed