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Number of ways in which AAABBB can be placed in the squares of figure as shown so that no row remains empty is ?

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Important Questions on Permutation and Combination

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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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The largest non-negative integer k such that 24k divides 13! is
EASY
The sum of the digits in the unit's place of all the 4 - digit numbers formed by using the numbers 3, 4, 5 and 6, without repetition is :
HARD
All possible numbers are formed using the digits 1, 1, 2, 2, 2, 2, 3, 4, 4  taken all at a time. The number of such numbers in which the odd digits occupy even places is
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The number of all 3-digits numbers abc (in base 10) for which 10 is
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In how many different ways can the letters of word CANDIDATE can be arranged in such a way that the vowels always come together?
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If all the words, with or without meaning, are written using the letters of the word QUEEN and are arranged as in English dictionary, then the position of the word QUEEN is:
EASY

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)

EASY
If Pr+656:Pr+3=30800:154 , then r is equal to
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How many ways are there to arrange the letters of the word EDUCATION so that all the following three conditions hold?
- the vowels occur in the same order EUAIO,
- the consonants occur in the same order DCTN,
- no two consonants are next to each other.
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The number of 4 letter words (with or without meaning) that can be formed from the eleven letters of the word EXAMINATION is
EASY
The total number of permutations of n(>1) different things taken not more than r at a time, when each thing may be repeated any number of times is
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The number of four-digit numbers strictly greater than 4321 that can be formed using the digit 0,1,2,3,4,5 (repetition of digits is allowed) is:
HARD
If all the words (with or without meaning) having five letters, formed using the letters of the word SMALL and arranged as in a dictionary; then the position of the word SMALL is 
EASY
The number of 6 digit number that can be formed using the digits 0, 1, 2, 5, 7 and 9 which are divisible by 11 and no digit is repeated 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
EASY

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

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The number of distinct primes dividing 12!+13!+14! Is
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How many natural numbers n are there such that n!+10 is a perfect square ?
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Two girls and four boys are to be seated in a row in such a way that the girls do not sit together. In how many different ways can it be done?