Find the $9$ term from the end $( towards\ the\ first\ term)$ of A.P. $5,\ 9,\ 13,\ .......\ 185$.


Given: An A.P. $5,\ 9,\ 13,\ .......\ 185$.

To do: To find the $9^{th}$ term from end.

Solution:

Given A.P. is $5,\ 9,\ 13,\ ....\ 185$

To find the $9^{th}$ term from end:

On rearranging the A. P.

$185,\ 181,\ ......,\ 13,\ 9,\ 5$

First term $=a=185$

Common difference $=d=a_2-a_1=181-185=-4$

$n^{th}$ term in an A. P $=a_n=a+( n-1)d$

$a = 185$; $d=-4;$ $n=9$

$9^{th}$ term$=a_9=a+( 9-1)d$

$=185+8\times( - 4)$

$=185-32$

$=153$

Therefore required $9^{th}$ term from the end$=153$.

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Updated on: 10-Oct-2022

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