Challenging Problems

Most students enjoy solving challenging problems to improve their problem solving and mathematical skills. Posting these kinds of problems is one of the best ways of keeping students informed about new challenging problems. For this, from time to time we will post new sets of challenging problems in this page. Notice that each item, that will be posted by us, will contain information about the source from which we obtain that item 

NOTE: I am posting these problems to introduce challenging problems in mathematics for those who are interested in learning mathematics through such problems. Do not  try  to send your solutions to the given addresses. I include all details for the sake of Copy Right.