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.