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

Dear Student!

Here is the answer to your query.

To find 20^th term from the last of the A. P. 3, 8, 13 ... 253

we have to find 20^th term of the reverse A. P. i.e.  253  ... 13, 8, 3

In the new A.P. first term a = 253 and common difference d = 3 – 8 = –5

We know that

a_n = a + (n – 1) d

⇒ a₂₀ = 253 + (20 – 1) (–5)

 = 253 + 19 × (–5)

 = 253 – 95 = 158

Hence 20^th term from the last of the A.P. 3, 8, 13 ... 253  is 158.

Cheers!