How many three digit numbers are divisible by 7.

The list of 3 digit numbers divisible by 7 is:

105, 112, 119,…,994

Here a = 105, d = 112 – 105 = 7, a_n = 994

We know that

a_n = a + (n – 1)d

994 = 105 + (n – 1)7

⇒ 889 = (n – 1)7

⇒ 127 = n – 1

⇒ 128 = n

So, there are 128 three– digit numbers divisible by 7.