Quandaries
and Queries 

If A=(1,2,3,4,...) and B=(5,10,15,20,...), is A equivalent to B. Why or Why not ? 

Hi, By equivalent I expect that you are asking if there is a "onetone relationship" between the sets or a "perfect matching" between the sets. I see a matchng between the sets in this way.
Thus every positive integer n on the left is paired with the 5 times n on the right. Also if you have a number on the right it is a multiple of 5, that is if m is on the right then there is a positive integer k so that m = 5 k and thus m, on the right is matched with k on the left. Penny 

