Question

The sum of the interior angles of a polygon is ${1260}^o$. Find the number of sides.

Answer 1

We know that, Sum of measures of all interior angles of polygons $=(2n-4)\times {90}^{\circ }$
Given, interior angle $={1260}^{\circ }$
$\begin{array}{c}1260=(2n-4)\times {90}^{\circ }\\ 1260/90=2n-4\\ 14=2n-4\end{array}$
By transposing we get,
$\begin{array}{c}2n=14+4\\ 2n=18\\ n=18/2\\ n=9\end{array}$
Therefore, the number of sides in a polygon is 9 .