Question

Find n(A) of the following set
A={101,102,103,104,...,121}

Answer 1

n(A) = 121-101+1 = 21

I used the formula:
[(the last - the first) divided by ratio ]+1

The answer to your question is n(A) = 21.
I hope that this is the answer that you were looking for and it has helped you.