How many numbers of two digit are divisible by 3?
Two digit numbers divisible by 3 are 12, 15, 18,… ,99
Hence, a= 12, ,d=3
an= a + (n -1)d
99= 12(n -1)3
99= 9 = 3n
n=30
Hence, the total numbers of two digit divisible by 3 are 30.