Permutations and Combinations
A four digit number is called a doublet if any of its digit is the same as only one neighbour. For example, 1221 is a doublet but 1222 is not. Number of such doublets are :
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Two variants of a test paper are distributed among 12 students. Number of ways of seating of the students in two rows so that the students sitting side by side by not have identical papers & those sitting in the same column have the same paper is :
How many 3-digit even numbers can be made using the digits 1,2,3,4,6,7 if no digit is repeated?
If 5 maths, 3 physics, 2 chemistry books are arranged in a shelf so that all physics books together and chemistry do not come together, then possible number of arrangements is?
A double-decker bus has 5 empty seats in the upstair and 5 empty seats in the downstair. 10 people board the bus of which, 2 are old people and 3 are children. The children refuse to take seats down stair while old people insist to stay down stair. In how many different arrangements can the 10 people take seats in the bus?
Write all possible 3-digits numbers using the digits 3,1 and 5. Repetition of digits is not allowed.
Number of 4 digit numbers of the form N=abcd which satisfy following three conditions (i) 4000≤N<6000 (ii) N is multiple of 5 (iii) 3≤b<c≤6 is equal to
Total 5 digit number divisible by 3 can formed using 0, 1,2,3,4,5 if repetition of digits is not allowed.
In how many ways can a team of 3 boys and 3 girls be selected from 5 boys and 4 girls?