Question

In an A.P., a = −36, d = 18 and l = 36, then n is ______.

विकल्प

• 10

• 5

• 15

• 20

Answer 1

In an A.P., a = −36, d = 18 and l = 36, then n is 5.

Explanation:

Let nth be the last term.

By formula,

a_n = a + (n − 1)d

Substituting values we get:

⇒ 36 = −36 + (n − 1)18

⇒ 36 = −36 + 18n − 18

⇒ 36 + 36 + 18 = 18n

⇒ 18n = 90

⇒ n = `90/18`​ = 5.