CBSE NCERT Solutions Chapter 5 Arithmetic Progressions Exercise 5.2 Question 13
13. How many three digit numbers are divisible by 7?
We have AP starting from because it is the first three digit number divisible by .
AP will end at because it is the last three digit number divisible by .
Therefore, we have AP of the form
Let is the nth term of AP. We need to find n here.
First term = a = 105
Common difference = d = 112 - 105 = 7
Using formula , to find nth term of arithmetic progression, we can say that
It means is the 128th term of AP. Therefore, there are terms in AP. In other words, we can also say that there are 128 three digit numbers divisible by 7.