Permutations & Combinations
24 JEE Main questions · Maths
Counting strictly increasing functions
The number of strictly increasing functions from the set to the set such that for , is equal to:- (1)21
- (2)27
- (3)22
- (4)28
We corrected a printing error in the original paper
Source printed the second set as “” (parentheses instead of set braces).
Counting ordered pairs
Let . If the number of elements in such that is a multiple of 5 is and the number of elements in such that is a square of a prime number is , then is equal to .Exponent of prime in factorial
The largest , for which divides , is:- (1)16
- (2)18
- (3)15
- (4)19
Selection of points on triangle sides
Let be a triangle. Consider four points , , , on the side , five points , , , , on the side and four points , , , on the side . None of these points is a vertex of the triangle . Then the total number of pentagons, that can be formed by taking all the vertices from the points , , , , is .Counting subsets
Let be the set of the first 11 natural numbers. Then the number of elements in is .Arrangements with repeated letters
The number of 4-letter words, with or without meaning, which can be formed using the letters PQRPQRSTUVP, is .Distribution of identical objects
The number of ways, in which 16 oranges can be distributed to four children such that each child gets at least one orange, is- (1)429
- (2)384
- (3)403
- (4)455
Counting numbers by digits
Let denote the set of 4-digit numbers such that and denote the set of 5-digit numbers having product of its digits equal to 20. Then is equal to .Counting numbers with divisibility
The number of numbers greater than 5000, less than 9000 and divisible by 3, that can be formed using the digits 0, 1, 2, 5, 9, if the repetition of the digits is allowed, is .Rank of a word in dictionary
The letters of the word “UDAYPUR” are written in all possible ways with or without meaning and these words are arranged as in a dictionary. The rank of the word “UDAYPUR” is:- (1)1580
- (2)1578
- (3)1579
- (4)1581
Exponent of a prime in factorial
The largest value of , for which divides , is- (1)13
- (2)11
- (3)12
- (4)14
Arrangements with repeated digits
Let . Let be the number of 9-digit numbers formed using the digits of the set such that only one digit is repeated and it is repeated exactly twice. Let be the number of 9-digit numbers formed using the digits of the set such that only two digits are repeated and each of these is repeated exactly twice. Then,- (1)
- (2)
- (3)
- (4)
Arrangements of persons
Three persons enter in a lift at the ground floor. The lift will go upto floor. The number of ways, in which the three persons can exit the lift at three different floors, if the lift does not stop at first, second and third floors, is equal to .Arrangements with each digit used
The number of seven-digit numbers, that can be formed by using the digits 1, 2, 3, 5 and 7 such that each digit is used at least once, is;- (1)15400
- (2)17800
- (3)16800
- (4)29400
Properties of binomial coefficients
If for , then equals:- (1)31
- (2)32
- (3)33
- (4)34
Triangles from polygon vertices
Let denote the total number of triangles formed by joining the vertices of an -sided regular polygon. If , then the sum of all distinct prime divisors of is:- (1)7
- (2)8
- (3)5
- (4)6
We corrected a printing error in the original paper
Source printed “an -side regular polygon”.
Arrangements with restrictions
The number of ways, of forming a queue of 4 boys and 3 girls such that all the girls are not together, is:- (1)5040
- (2)3050
- (3)3410
- (4)4320
Non-negative integer solutions
Let are non-negative integers and . The is equal to:- (1)121
- (2)124
- (3)144
- (4)169
Counting one-one functions
Let . The number of one-one functions such that , and , is .Counting game sequences
Two players and play a series of games of badminton. The player, who wins 5 games first, wins the series. Assuming that no game ends in a draw, the number of ways, in which player wins the series is .Selection with restrictions
A box contains 5 blue, 6 yellow and 4 red balls. The number of ways, of drawing 8 balls containing at least two balls of each colour, is:- (1)4100
- (2)4140
- (3)4230
- (4)4290
Selection and arrangement of letters
The number of 4-letter words, with or without meaning, each consisting of two vowels and two consonants that can be formed from the letters of the word INCONSEQUENTIAL, without repeating any letter, is:- (1)2670
- (2)2840
- (3)2920
- (4)3600
Distribution into groups and floors
A building has ground floor and 10 more floors. Nine persons enter in a lift at the ground floor. The lift goes up to the floor. The number of ways, in which any 4 persons exit at a floor and the remaining 5 persons exit at a different floor, if the lift does not stop at the first and the second floors, is equal to:- (1)2184
- (2)3064
- (3)7056
- (4)11340
Distribution into non-empty groups
A person has three different bags and four different books. The number of ways, in which he can put these books in the bags so that no bag is empty, is- (1)18
- (2)36
- (3)39
- (4)72
