Question

Question 4
Which term of the A.P
$3,8,13,18,\dots$ is 78?

Answer 1

$GiventheA.Pis3,8,13,18,\dots$
Here,
$a=3d=a_2-a_1=8-3=5Let{n}^{th}termofthisA.P.be78.$

$The{n}^{th}termanA.P.isgivenby:$
$a_n=a+(n-1)d\Rightarrow 78=3+(n-1)575=(n-1)5(n-1)=15n=16Hence,the{16}^{th}termofthisA.P.is78.$