Find the sum of all two digit natural numbers which are divisible by 4.

The sum of series of the two digit natural numbers that are divisible by 4 is a = 12, d = 16 - 12 = 4 and l = 96. Let 96 be nth term then, ⇒ 96 = 12 + 4(n - 1) ⇒ 96 - 12 = 4n - 4 ⇒ 84 = 4n - 4 ⇒ 4n = 84 + 4 ⇒ 4n = 88 ⇒ n = 22. By formula S n = ⇒ S 22 = ⇒ S 22 = 11[24 + 84] ⇒ S 22 = 11 × 108 ⇒ S 22 = 1188. Hence, the sum of all two digits natural numbers which are divisible by 4 is 1188.