Question

How many terms are there in the AP 41, 38, 35, ….,8?

Answer 1

In the given AP, a = 41 and d = (38-41) = -3
Suppose that there are n terms in the given AP.
Then T_n  = 8 

⇒ a + (n-1) d = 8

⇒ 41+ (n-1) × (-3) = 8

⇒ 44- 3n =8

⇒ 3n = 36

⇒ n=12

Hence, there are 12 terms in the given AP.