Question

Which term of the AP 72, 63, 54, ... is 0?

Options

• 8th

• 9th

• 10th

• 11th

Answer 1

9th

Explanation:

First term a = 72 and common difference d = 63 – 72 = –9.

nth term: T_n = a + (n – 1)d 

= 72 + (n – 1)(–9) 

= 81 – 9n

Set T_n = 0

⇒ 81 – 9n = 0

⇒ n = 9