Question

Find the number of terms in the following A.P. 

7,13,19, …………….. ,205

Answer 1

Given : 7, 13, 19 …………….., 205 are in A.P 

a = 7, d = 6 

Let a_n = 205 

a + (n – 1)d = 205 7 + (n – 1)6 = 205 . 

(n- 1)6 = 205 -7 (n-1)6 =198 (n – 1) = 

33 ⇒ n = 34 

Number of terms in the given A.P is 34.