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The number of square matrices of order 5 with entries from the set {0,1}, such that the sum of all the elements in each row is 1 and the sum of all the elements in each column is also 1, is 

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Important Questions on Permutation and Combination

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JEE Main
IMPORTANT
Let S=1,2,3,5,7,10,11. The number of non-empty subsets of S that have the sum of all elements a multiple of 3, is _____ .
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IMPORTANT
Let x and y be distinct integers where 1x25 and 1y25. Then, the number of ways of choosing x and y, such that x+y is divisible by 5 , is _____ .
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IMPORTANT

The number of numbers, strictly between 5000 and 10000 can be formed using the digits 1,3,5,7,9 without repetition, is

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IMPORTANT
Suppose Anil's mother wants to give 5 whole fruits to Anil from a basket of 7 red apples, 5 white apples and 8 oranges. If in the selected 5 fruits, at least 2 orange, at least one red apple and at least one white apple must be given, then the number of ways, Anil's mother can offer 5 fruits to Anil is _____ .
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IMPORTANT
If all the six digit numbers x1x2x3x4x5x6 with 0<x1<x2<x3<x4<x5<x6 are arranged in the increasing order, then the sum of the digits in the 72th  number is _______.
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IMPORTANT
Five digit numbers are formed using the digits 1, 2, 3, 5, 7 with repetitions and are written in descending order with serial numbers. For example, the number 77777 has serial number 1. Then the serial number of 35337 is
HARD
JEE Main
IMPORTANT
The letters of the word OUGHT are written in all possible ways and these words are arranged as in a dictionary, in a series. Then the serial number of the word TOUGH is :