Question

___${}^{th}$ term of AP 3, 8, 13, 18,...... is 78.

• A. 12
• B. 14
• C. 16
• D. 18

Answer 1

The correct option is C 16

Given: $n^{th}$ term of the AP = 78
Common difference(d) = 5
First term(a) = 3

$n^{th}$ term of AP is,
$T_n=a+(n-1)d$
$\Rightarrow 78=3+(n-1)5$
$\Rightarrow 5(n-1)=78-3$
$\Rightarrow n-1=\frac{75}{5}=15$
$\Rightarrow n=16$