Alex’s Marble Bridge

Alex and Bernice build a marble track on the garden table with Mum. They rest a strip of card across two wooden blocks. It makes a bridge over a gap in the course.

The red marble rolls onto the card, and the middle begins to sag. Alex catches the marble before it drops. Bernice notices how low the paper bridge has bent.

They try holding the card level. That leaves no hands free for the game. “Could you change the card's shape?” asks Mum. “Keep the same piece of card and the wooden blocks.”

Bernice folds a narrow edge upwards along each long side of the card. Alex presses the folds carefully, then they put the new bridge back across the same gap.

Mum holds the marble ready while the children check both ends of the bridge. The folded sides stand above the track. The middle no longer bends down so easily.

Alex releases the marble. It rolls across the card and reaches Bernice. She catches it beyond the far block. Nobody has needed to hold the bridge in place.

They send the marble across again from the opposite end and watch its path. The sides help keep it on the bridge while the folded card holds its shape above the gap.

After playing, they save their bridge with the two blocks and the marble. “We changed its shape, not its size,” says Bernice, showing Mum the folds that made the difference.