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Let x1,x2,x3,,xk are the total divisors of positive integer n. If i=1kxi=93 and i=1k1xi=9350, then the value of k is

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Important Questions on Permutation and Combination

EASY
The sum of factors of 8! which are odd and are of the form 3m+2, where m is a natural number, is
MEDIUM
A natural number has prime factorization given by n=2x3y5z, where y and z are such that y+z=5 and y-1+z-1=56,y>z. Then the number of odd divisors of n, including 1, is:
MEDIUM
The total number of 3-digit numbers whose sum of digits is 10, is ..........
MEDIUM

If α and β are the greatest divisors of nn2-1 and 2nn2+2 respectively for all nN, then αβ=

HARD
A positive integer k, is perfect if the sum of its positive divisors equals 2k. If n, is a perfect number, then the sum of the reciprocal of its positive divisors
HARD
If the integers from 1 to 2021 are written as a single integer like 1239101120202021, then the 2021st digit (counted from the left) in the resulting number is
HARD
Ari chooses 7 balls at random from n balls numbered 1 to n. If the probability that no two of the drawn balls have consecutive numbers equals the probability of exactly one pair of consecutive numbers in the chosen balls, find n.
MEDIUM

Consider the following statements
i. Number of ways of placing 'n' objects in k bins kn ) such that no bin is empty is Ck-1(n-1)

ii. Number of ways of writing a positive integer " n ' into a sum of k positive integers is Ck-1(n-1)

iii. Number of ways of placing ' n ' objects in k bins such that at least one bin is non-empty is Ck-1(n-1)

iv. Ckn-Ckn-1=Ck-1(n-1)

HARD
Let N be the least positive integer such that whenever a non-zero digit C is written after the last digit of N, the resulting number is divisible by C. The sum of the digits of N is
MEDIUM
In a hotel, four rooms are available. Six persons are to be accommodated in these four rooms in such a way that each of these rooms contains at least one person and at most two persons. Then the number of all possible ways in which this can be done is_____
MEDIUM
Let m=9n2+54n+809n2+45n+549n2+36n+35. The greatest positive integer which divides m, for all positive integers n is
HARD
If N is the number of triangles of different shapes (i.e. not similar) whose angle are all integers (in degrees), what is N100?
MEDIUM
The number of different garlands, that can be formed using 3 flowers of one kind and 3 flowers of other kind, is
HARD
Let A={1,2,3,4,5,6,7,8}, B={9,10,11,12,13,14,15,16} and C={17,18,19,20,21,22,23,24}. Find the number of triples (x,y,z) such that xA, yB, zC and x+y+z=36.
HARD
The number of points, having both co-ordinates as integers, that lie in the interior of the triangle with vertices 0, 0, 0, 41 and 41, 0 is
MEDIUM
Let n be a non-negative integer. Then the number of divisors of the form 4n+1 of the number 1010·1111·1313 is equal to _____.
EASY
The number of ways in which 9 persons can be divided into three equal groups is
MEDIUM

If a is the number of all even divisors and b is the number of all odd divisors of the number 10800, then 2a+3b=

MEDIUM
Number of divisors of the form 4n+2,n0 of the integer 240 is