JAMB 2016 · UTME · Q29

Binary operations

$\otimes$	$p$	$q$	$r$	$s$
$p$	$r$	$p$	$r$	$p$
$q$	$p$	$q$	$r$	$s$
$r$	$r$	$r$	$r$	$r$
$s$	$q$	$s$	$r$	$q$

The identity element with respect to the operation shown in the table is

Worked solution (try it first)

The identity leaves every element unchanged, so its row and its column must repeat the headings $p, q, r, s$ .
The row for $q$ reads $p, q, r, s$ , and so does the column under $q$ .
So the identity is $q$ , option B.

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