Enjoyable questions and problems

There is a circular park with a walking path going all round. There is also a straight path – the central walkway from A to B. See the diagram below: Suppose you walk the straight path from A to B, which is 100 yards long. Your friend walks from A all the way around the circular path till he comes back to A. How many yards will your friend’s walk be? His walk cannot be less than 200 yards. Can you guess why? It is actually more than 300 yards. How do you find out the length of your friend's walk? Can you discuss it with someone? 

  Think of a number between 1 and 5. Write down X = that number Multiply X by 6 and write down the product as A = that product Multiply X by 4 and write down the product as B = that product Add A and B and tell me the sum. I can then tell you what is X