Question

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

Answer 1

Solution: a = 3, d = 5
253 = 3 + 5(n-1)
Or, 5(n-1) = 250
Or, n-1 = 50
Or, n = 51
So, the 20th term from the last term = 51 – 19 = 32nd term
Now, n₃₂ = 3 + 5x31 = 158