Question:

Let W denote the words in the English dictionary. Define the relation $R $ by : $R =\{ (x,y), \in\, W \times \,W$ : the words $x$ and $y$ have at least one letter in commona$\}$ Then R is

Updated On: Jun 23, 2023
  • reflexive, not symmetric and transitive
  • not reflexive, symmetric and transitive
  • reflexive, symmetric and not transitive
  • reflexive, symmetric and transitive
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The Correct Option is C

Solution and Explanation

Let $w \in W$ then $(w, w) \in \: R \: \therefore \: R$ is reflexive. Also if $w_1, w_2 \in\,W $ and $ (w_1,w_2) \in\, R,\,$ then $\, (w_2, w_1) \in\, R.\, \therefore\, R $ is symmetric. Again Let $w_1 = I N K, w_2$ = L I N K, $w_3 $ = L E T Then $(w_1, w_2) \in\, R$ [$\because$ I, N are the common elements of $w_1, w_2](w_2,w_3)\in\,R$ [$\because$ L is the common element of $w_2, w_3$] But $(w_1, w_3) \notin \,R$ [$\because$ there is no common element of $w_1,, w_3$] $\therefore $ R is not transitive.
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Concepts Used:

Functions

A function is a relation between a set of inputs and a set of permissible outputs with the property that each input is related to exactly one output. Let A & B be any two non-empty sets, mapping from A to B will be a function only when every element in set A has one end only one image in set B.

Kinds of Functions

The different types of functions are - 

One to One Function: When elements of set A have a separate component of set B, we can determine that it is a one-to-one function. Besides, you can also call it injective.

Many to One Function: As the name suggests, here more than two elements in set A are mapped with one element in set B.

Moreover, if it happens that all the elements in set B have pre-images in set A, it is called an onto function or surjective function.

Also, if a function is both one-to-one and onto function, it is known as a bijective. This means, that all the elements of A are mapped with separate elements in B, and A holds a pre-image of elements of B.

Read More: Relations and Functions