Find the 20th term from the last term of the AP: 3, 8, 13, …, 253.

Given:

Given A.P. is $3, 8, 13,…, 253$. 

To do:

We have to find the 20th term from the last term of the given AP. 

Solution:

In the given A.P.,

$a_1=3, a_2=8, a_3=13$

First term $a_1 = a= 3$, last term $l = 253$

Common difference $d = a_2-a_1 = 8 - 3 = 5$

We know that,

nth term from the end is given by $l - (n - 1 ) d$.

Therefore,

20th term from the end $= 253 - (20 - 1) \times 5 = 253 - 19 \times 5 = 253 - 95 = 158$.

The 20th term from the end of the given A.P. is $158$.