Question

How many natural numbers less than 1000 are not divisible by 5 and 7?

Answer 1

An=1,2,3,4,5,…………,1000.

So total number of natural numbers=1000

The number of numbers divisible by 15 will be

An1= 15,30,45,60……,990

=>990=[15+(n-1)*15] =>n=66…..(1)

The number of numbers divisible by 10 will be