Question

Which terms of the $A.P3,8,13,\mathrm{18....}$ find the position is $78$

Answer 1

Considering the series to be:

$3,8,13,18,.........$

$a=3,d=5$

$T_n=a+(n-1)d$

$78=3+(n-1)5$

$75=(n-1)5$

$15=n-1$

$n=16$