Paper-Cup Tower

Japanese name: 紙コップタワー

Materials

Give each group the same number of cups and equally sized building space. Demonstrate by standing two cups upside down and placing a third across the gap above them.
Allow three minutes to build a shape of the group's choice. Agree either to place cups one person at a time or to divide responsibility for different parts.
Build a tower that stands without hands, tape or glue. Rebuild in your own area if it falls. Do not touch another group's work.
On the signal, remove all hands. A tower that stands for five seconds is complete. If comparing height, measure from the floor to its highest point. For preschool children, aim for every group to finish.
Nest the cups to clear the area, then discuss and build a second tower. Each group shares one idea for stability. Count all the cups before finishing.

Preschool children: 3–6 cups. Younger primary school children: 20 cups. Older primary school children: add a design discussion.