Which term of the AP 72, 68, 64, 60, ... is 0?

In the given AP, the first term = a = 72

Common difference = d = 68 - 72 = - 4

To find: place of the term 0.

So, let a_n = 0

Since, we know that

a_n = a + (n - 1) × d

∴ 0 = 72 + (n - 1) × (-4)

⇒ 0 - 72 = - 4n + 4

⇒ - 72 - 4 = - 4n

⇒ - 76 = - 4n

⇒ n = 76/4

⇒ n = 19

∴ 19^th term of the AP is 0.