Triangle is the strongest shape a structure can have to build a bridge. It is the strongest shape because any added force is evenly spread through all three sides.
Squares or cubes also can be strengthened by adding a diagonal pieces across the middle making it two triangles linked together. Here then i thought kids on a simple illustration activities of the strongest shape and show them.
triangle shape 
square shape
Then to make it more interesting, we make a build game contest to compete whose tower the strongest.
To construct the towers, we used colourful popsicle sticks which you can buy at Mr DIY and use cellophane tape to sticks them together. We avoid using glue because it would be messy and more time needed to let it dry.
The strongest tower could withstand more books and should be the winner.
After completion, we tested the robustness of each tower by putting slowly books on top of it.
The strongest towers as follows:
- Mom + hadien
- Hadeef
- Aliesha