Let A be the event that a positive integer 1000 or less 
is exactly divisible by 77.

Let B be the event that a positive integer 1000 or less 
is exactly divisible by 49.

We want:



To find N(A) we divide 1000/77 = 12.98701299, and round 
down to 12.

So 

To find N(B) we divide 1000/49 = 20.40816327, and round 
down to 20.

So 

For an integer to be divisible by both 77 and 49 it has
to be divisible by 77*49 or 539, and only one positive
integer in the first 1000 positive integer that is divisible
by 539 is 539 itself.  So N(A and B) = 1

So 



becomes:



Answer: 0.031

Edwin