Question

In an AP if a = –7.2, d = 3.6, an = 7.2, then n is
(A) 1 (B) 3 (C) 4 (D) 5

Answer 1

The answer is 1.As if we will divide the following equation then we will get 1

Answer 2

The value of n is (D) "5".

Step-by-step explanation:

We have,

a = - 7.2, d = 3.6 and $a_{n} =7.2$

To find, the value of n =?

We know that,

$a_{n} =a+(n-1)d$

∴ $-7.2+(n-1)(3.6)=7.2$

⇒ $(n-1)(3.6)=7.2+7.2=14.4$

⇒ $n-1=\dfrac{14.4}{3.6} =4$

⇒ n = 4 + 1 = 5

Hence, the value of n is (D) "5".