Chapter 5: Arithmetic Progressions

Example 6. Find the sum of first 30 terms of an A. P. whose n^th term is 2 + 1/2n

Solution:-

t_n = 2 + 1/2n

t_{n - 1} = 2 + 1/2( n- 1)

t_n - t_n - 1 = 2 + 1/2n - 2 - 1/2(n - 1)

d = 1/2

a = t₁ = 2 + 1/2 X 1 = 5/2

n = 30