Question

Find the eighteenth term of the A.P. $1,7,13,19,..........$

Answer 1

Let $a$ be the first term and $d$ be the common difference of given AP.
Hence $a=1$ and $d=7-1=6$.
$t_n=a+(n-1)d$
$\Rightarrow t_{18}=1+17\times 6$
$\Rightarrow t_{18}=1+102$
$\Rightarrow t_{18}=103$