Find the number of all three digit natural numbers which are divisible by 9.
Let the three digit numbers divisible by 9 are
108, 117, 126,… ,999
a=108, d=9, last term, l= 999
Number of terms, n = +1
= + 1
= +1
=100
Hence, the number of all three digit natural numbers which are divisible by 9 are 100