For what value of $n$, the nth term of the two AP: $3,\ 8,\ 13,.......$ and $19,\ 22,\ 25,......$ will be equal?


Given: nth term of the two AP: $3,\ 8,\ 13,.......$ and $19,\ 22,\ 25,......$ will be equal.

To do:  To find the value of $n$.


 Solution:


$A_1 =3,\ 8,\ 13$

$a_{n_{1}}=a+(n−1)d$

$=3+(n−1)5$                 $(here\ a=3,\ d=5)$

$=3+5n−5$

$=5n−2$


$A_2=19,\ 22,\ 25$

$a_{n_{2}}=a+(n−1)d$

$=19+(n−1)3$                      $(here\ a=19,\ d=3)$

$=19+3n−3$

$=16+3n$


$\because a_{n_{1}}=a_{n_{2}}$  $( As\ per\ question)$ 
$\Rightarrow 5n−2=16+3n$

$\Rightarrow 5n−3n=16+2$

$\Rightarrow 2n=18$

$\Rightarrow n=9$

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Updated on: 10-Oct-2022

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