Question

in an ap3. 8, 13 .......253 find 20th term from last​

Answer 1

Answer:

a = 3, d = 5

Now, 253 = a + (n + 1) d

⇒ 253 = 3 + (n -1) x 5

⇒ 253 = 3 + 5n – 5 = – 2

⇒ 5n = 253 + 2 = 255

⇒ n = 255/5 = 51

Therefore, 20th term from the last term = 51 – 19 = 32

a32 = a + 31d

        = 3 + 31 x 5

        = 3 + 155 = 158

Thus, required term is 158

Hope it helps u.

Answer 2

Here, from last
a = 253
d = 8-3 = 5
we know that,
An = a + (n-1)d
A20 = 253 + (20-1)5
= 253 + 19×5
= 253 + 95
= 348
Hopes it's helps you,
thanks