Question 1116438
.
<pre>
If "n" is the number of students in the class, then the number of possible pairs is {{{(n*(n-1))/2}}}.


Your equation is


{{{(n*(n-1))/2}}} = 45,   or   n*(n-1) = 90,  which implies  n = 10.


<U>Answer</U>.  There are 10 students in the class.
</pre>