A bridge is a simple idea: stretch a road from one side of a river to another, and people can cross without having to swim. But this bridge takes it one step further. Our friends in Midland, Michigan are home to a three-way bridge, which they call the Tridge. It’s a wooden footbridge (no cars!) that crosses the Chippewa River once and the Tittabawassee River twice. Here we see it from above. The bridge is just 8 feet wide, and each spoke is just 180 feet long from the center to the riverbank, less than 1/20 of a mile. It’s not that far, but definitely easier to walk it than swim.
Wee ones: If you drew straight lines to connect the Tridge’s ends to make a 3-sided shape, what shape would that be?
Little kids: If you walked on the bridge from the left side, reached the middle and turned right, which part would you then walk on? Point to it. Bonus: If you lay across the 8-foot-wide Tridge, how much taller would you need to be to stretch across? Find out your height to the closest foot!
Big kids: Look at the cars in the upper right — they look so small! About how many of them look like they could fit end to end from the water’s end to the middle of the Tridge? Bonus: How long is 1/10 of a mile? (Reminder if needed: A mile has 5,280 feet.)
The sky’s the limit: If you start on the left, cross the bridge to the upper right corner, then cross from there to the bottom right, then cross again to end up at your start, will 10 full trips like that give you a mile of walking?
Wee ones: A triangle.
Little kids: The bottom right part. Bonus: Different for everyone…subtract your height in feet from 8.
Big kids: In reality you could fit about 9 of them. Bonus: 528 feet.
The sky’s the limit: Yes. You walk 6 of these 180-foot spokes in 1 full trip, or 1,080 feet. So 10 trips will require walking 10,800 feet, which is more than the 5,280 feet in a mile – in fact, it’s more than 2 miles!
Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.