Question

How many two digits numbers are divisible by 3 ?

Answer 1

Total no. of two digit no.'s divisible by 3 are 30.

Answer 2

The list of two-digit numbers divisible by 3 are :

12,15,18...,99

Here, a= 12 ,d = 3, $a_n$= 99

$a_n = a +(n-1)d,$

99= 12+(n-1) ×3

87 =(n-1)×3

$n-1 = \frac{87}{3} = 29$

n = 29+1 =30