In this town, houses are built with one room for each person. There are some families of seven people living in the town. In how many different ways can they build their houses?
Andrew decorated 20 biscuits to take to a party. He lined them up and put icing on every second biscuit and different decorations on other biscuits. How many biscuits weren't decorated?
What happens if you join every second point on this circle? How about every third point? Try with different steps and see if you can predict what will happen.