Question

Find the 20th term from the last term of an ap 3 8 13 and 253

Answer 1

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

Answer 2

CH:-A.P

Given data:-

A.P=3,8,13......253

a=3

d=a2-a1

=8-3

=5

l=253

n=20

nth term from the end={l-(n-1)d}

since,20th term from end={253-(20-1)5}

=(253-95)

=158 ans

( for solving these type of question you have to first write the given data and put there values in the formula )