Answer 1

The first three digit natural number divisible by 5 is 100.
Common difference d = 5
Last three digit natural number divisible by 5 is 995
We know that,

t_n = a + (n -1) d
995 = 100 + (n -1) 5
895 = 5 (n -1)
179 = n -1
 n =180
Hence, there are 180 three digit natural numbers divisible by 5.