You put two 1 dollar coins on a table, such that they touch each other (see the figure). While you fix the lower coin with your finger, you will turn the upper around it (without slipping). Somewhat later the moving coin will be back in his original position. How many rotations on his midpoint did the moving coin make?

If you would fold a letter in two fifty times, how thick should the enveloppe be that can fit the letter? Assume that the thickness of a piece of paper is about 0.05 mm.

What will be the probability that the price of a randomly choosen share that can be bought on the euronext stock exchange in Amsterdam, starts with the digit 1?