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 20th term from the last of the A. P. 3, 8, 13 ... 253
we have to find 20th 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
an = a + (n – 1) d
⇒ a20 = 253 + (20 – 1) (–5)
= 253 + 19 × (–5)
= 253 – 95 = 158
Hence 20th term from the last of the A.P. 3, 8, 13 ... 253 is 158.
Cheers!