Find the middle term of the AP 1, 8, 15....505.
Ans: Middle terms
a + (n-1)d = 505
a + (n-1)7 = 505
n - 1 = 504/7
n = 73
∴ 37th term is middle term
a_{37} = a + 36d
= 1 + 36(7)
= 1 + 252
= 253