Choose the correct answer in each of the following questions:
Question:

Choose the correct answer in each of the following questions:

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

(a) 8th

(b) 9 th

(c) 10 th

(d) 11 th

Solution:

The given AP is 72, 63, 54, … .

Here, a = 72 and d = 63 − 72 = −9

Suppose nth term of the given AP is 0. Then,

$a_{n}=0$

$\Rightarrow 72+(n-1) \times(-9)=0 \quad\left[a_{n}=a+(n-1) d\right]$

$\Rightarrow-9 n+81=0$

$\Rightarrow n=\frac{81}{9}=9$

Thus, the 9th term of the given AP is 0.

Hence, the correct answer is option B.