How many two digit numbers are divisible by 3.
We know, an = a + (n – 1)d⇒ 99 = 12 + (n – 1) 3⇒ 99 = 12 + 3n – 3⇒ 99 = 9 + 3n⇒ 3n = 90⇒ n = 30Hence, there are 30 two-digit numbers which are divisible by 3.