Question

Find the eighteenth term of the A.P

$7,13,19,25,....$

Answer 1

We have $t_1=7,t_2=13,t_3=19,t_4=\mathrm{25....}$
$d=t_2-t_1=13-7=6$
The common difference, $d=6$ and first term, $a=7$
We know that, $t_n=a+(n-1)d$
$\therefore$ $t_{18}=7+(18-1)\times 6$
$\therefore$ $t_{18}=7+17\times 6$.
$\therefore$ $t_{18}=7+102$
$\therefore$ $t_{18}=109$
$\therefore$ the eighteenth term of the A.P is $109$