1.

If the numbers of different reflexive relations on a set A is equal to the number of different symmetric relations on set A, then the number of elements in A isA. 1B. 3C. 1 and 3D. 3 and 7

Answer» Correct Answer - B
Let there be n elements in set A. Then,
Number of different reflexive relations on `A=2^(n^(2)-n)`
Number of different symmetric relations on `A=2^((n^(2)+n)/(2))`
It is given that
`2^(n^(2)-n)=2^((n^(2)+n)/(2))`
`implies n^(2)-n=(n^(2)+n)/(2)impliesn^(2)-3n=0impliesn(n-3)=0impliesn=3`


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