Question

Find n(A) for A={0,1,2,3,...,2000}

Answer 1

There are 2001 items in that set.

So n(A) = 2001

We can individually count them all out, which is very slow and tedious, or we can use the formula
n-m+1

where,
m = starting value
n = ending value

In this case,
m = 0
n = 2000
So,
n-m+1 = 2000-0+1 = 2001

This formula only works if we increase the number by 1 each time (eg: 6, 7, 8, etc)