Question

Which term of the A.P $5,13,21,.....$ is $181$?

Answer 1

Consider the $A.P.$, $5,13,21,...$

The first term, $a=5$

The common difference, $d=13-5=8$

The $n^{th}$ term is $181$

The $n^{th}$ term is given by $a+(n-1)d$

$\Rightarrow 181=5+(n-1)8$

$\Rightarrow 181=5+8n-8$

$\Rightarrow 181=8n-3$

$\Rightarrow 184=8n$

$\Rightarrow n=23$

Hence, the ${23}^{rd}$ term of the A.P is $181$