Strong triangles

Ages 3 to 5 Read and do together · about 15 minutes

Read together

A square can wobble. A triangle stays firm.

Builders use triangles to make things strong.

Do it

1. Make a square from four craft sticks or straws joined at the corners with tape. Push it. It wobbles and bends.
2. Add one stick across the corners to make two triangles. Push again. It is firm.
3. Look for triangles in bridges, roofs, bicycle frames and swing sets.
4. Build a small tower using triangles and see how tall it can go.

Talk about it

• Why is the triangle stronger?
• Where have you seen triangles holding things up?

For the grown-up

A triangle cannot change shape without bending a side, so it is rigid. A four-sided frame can fold. That is why triangles appear in bridges, roof trusses and towers.

Mark as done

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Where this comes from

• NGSS Lead States, Next Generation Science Standards: For States, By States (National Academies Press, 2013), performance expectation K-2-ETS1-2 (develop a simple sketch, drawing or physical model to illustrate how the shape of an object helps it function)
• Mario Salvadori, Why Buildings Stand Up: The Strength of Architecture (W. W. Norton, 1980)

Written with AI assistance and checked against the sources listed. Please read it before sharing it with a child.