MEDIUM
JEE Main
IMPORTANT
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Let S be the set containing all 3×3 matrices with entries from -1,0,1. The total number of matrices AS such that the sum of all the diagonal elements of ATA is 6 is ______.

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Important Questions on Permutation and Combination

HARD
JEE Main
IMPORTANT
The number of functions f, from the set A=xN:x2-10x+90 to the set B=n2:nN such that fxx-32+1, for every xA, is _______.
MEDIUM
JEE Main
IMPORTANT
Let S be the set of all passwords which are six to eight characters long, where each character is either an alphabet from A,B,C,D,E or a number from 1,2,3,4,5 with the repetition of characters allowed. If the number of passwords in S whose at least one character is a number from 1,2,3,4,5 is α×56, then α is equal to
MEDIUM
JEE Main
IMPORTANT
A class contains b boys and g girls. If the number of ways of selecting 3 boys and 2 girls from the class is 168, then b+3g is equal to
MEDIUM
JEE Main
IMPORTANT
The number of matrices of order 3×3, whose entries are either 0 or 1 and the sum of all the entries is a prime number, is _______.
MEDIUM
JEE Main
IMPORTANT
The number of natural numbers lying between 1012 and 23421 that can be formed using the digits 2,3,4,5,6 (repetition of digits is not allowed) and divisible by 55 is _____.
HARD
JEE Main
IMPORTANT
Suppose r=02023r2·Cr2023=2023×α×22022, then the value of α is
MEDIUM
JEE Main
IMPORTANT
The number of 9 digit numbers, that can be formed using all the digits of the number 123412341 so that the even digits occupy only even places, is ______