EASY
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There are 15 points in a plane out of which 6 are collinear. Find the number of lines that can be formed from 15 points.

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Important Questions on Counting Principles

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How many number divisible by 5 of 6 digit can be made from the digit 2,3,4,5,6,7
EASY
If Prn=840 and Crn=35, then the value of r is equal to
MEDIUM

The number of (a, b, c), where a, b, c are positive integers such that abc = 30, is

EASY
If Cnr-1=36, Cnr=84 and Cnr+1=126 , then n=
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From 6 different novels and 3 different dictionaries, 4 novels and 1 dictionary are to be selected and arranged in a row on a shelf so that the dictionary is always in the middle. The number of such arrangements is:
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a,b,c are three particular speakers among the 10 speakers of a meeting. The number of ways of arranging all the 10 speakers on the dias in a row so that all the three speakers a,b,c do not sit together is
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In a group of 6 boys and 4 girls, a team consisting of four children is formed such that the team has atleast one boy. The number of ways of forming a team like this is
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How many numbers of four digits can be made by using the digits 3, 5, 6, 7, and 9?  (Repetition of digits is not allowed)

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In how many ways the letters of word 'MACHINE' can be arranged so that vowels will always be together?

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If S is a set with 10 elements and A=x, y:x, yS, xy , then the number of elements in A is
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A five-digit number divisible by 3 is to be formed using the numerals 0, 1, 2, 3, 4 and 5 without repetition. The total number of ways this can be done is
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The number of diagonals of a polygon with 15 sides is
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If P4n=20nP2 where P denotes the number of permutations, then n= ________
EASY
A password is set with 3 distinct letters from the word LOGARITHMS. How many such passwords can be formed?
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A committee of five members is to be formed out of 3 trainees, 4 professors and 6 research associates. In how many different ways can this be done if the committee should have all the 4 professors and 1 research associate or all 3 trainees and 2 professors?
HARD
Sum of last 30 coefficents in the binomial expansion of 1+x59 is
HARD
The number of 4 digit numbers without repetition that can be formed using the digits 1, 2, 3, 4, 5, 6, 7 in which each number has two odd digits and two even digits is
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If Pr+656:Pr+3=30800:154 , then r is equal to
MEDIUM
In how many different ways can the letters of word CANDIDATE can be arranged in such a way that the vowels always come together?