Or search by topic
"This was fun," we heard from many people who moved the circles around as they tried to find out how to rebuild the triangle so it faced in the opposite direction. Gerrit did very well to put into words what you needed to do:
"To change the triangle's direction with only three moves, move the outside bottom row balls to the second row from the top, and move the top ball to the bottom."
Easy when you know how!
Cut four triangles from a square as shown in the picture. How many different shapes can you make by fitting the four triangles back together?
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?