Index Card Bridge Test

What you need

• Paper, 10 index cards or paper strips (20 for easier version)
• Painter's tape, 20 centimeters (as much as you like for easier version)
• Crayons or markers, 1 marker for scoring (optional)
• Book, about 12
• Ruler, 1
• Coins, a pile

How to do it

Grown-up prep: Coins are a choking risk, so keep this activity away from toddlers and babies, and count the coins back into a jar at the end. Ollie says a paper bridge is a great way to learn how real bridges stay strong.

1. Stack the books into two piles that are exactly the same height.
2. Slide the piles apart until one ruler fits between them.
3. Measure out 20 centimeters of tape. That is all you get!
4. Build a bridge across the gap using your cards and tape.
5. Place coins one at a time on the middle of the bridge.
6. Write down how many coins your bridge held. That is your score!
7. Now redesign it. Try folding cards into beams, tubes, triangles or a zigzag.
8. Load the new bridge with coins until it sags. Count your score.
9. Compare your shapes. Which one held the most? Build again and beat it!

Play it again

• Shape showdown: build one bridge for each shape and see which holds the most coins.
• Wider gap: move the book stacks farther apart and see how far your bridge can reach.
• Team build: two people build one bridge together, with each person using half the cards.