Find the 20th term from the last term of the AP

Solution:

The AP is 3, 8, 13, ..., 253

Its first term = 3 and the common difference = 5.

Now, the AP in the reverse order will have the first term = 253 and the common difference = – 5.

The 20th term from the end of the AP (1)

= The 20 term of the AP in the reverse order

$=a+19 d$

$=253+19 \times(-5)=253-95=158$