KCET-2014-Mathematics-Paper
KCET 2014 Mathematics Paper
Question 1
Let S be the set of all real numbers. A relation R has been defined on S by aRb $\Leftrightarrow$ |a-b| $\le$ 1, then R is
Solution
The correct answer is Reflexive and Symmetric but not Transitive
Explanation
Given that aRb $\Leftrightarrow$ |a-b| $\le$ 1
∴ aRa $\Leftrightarrow$ |a-a| = 0 $\le$ 1
Therefore, R is reflexive.
Again, aRb $\Leftrightarrow$ |a-b| $\le$ 1
∴ bRa $\Leftrightarrow$ |b-a| $\le$ 1
⇒ |a-b| $\le$ 1, which is true
Therefore, R is symmetric.
Take a b = = 1 2, then |a-b| = |1-2| = 1
Take b c = = 2 3, then |b-c| = |2-3| = 1
But aRc = |a-c| = |1-3| = 2 > 1
Therefore, R is not transitive.
Hence R is reflexive and symmetric but not transitive.
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