What do you see all around your room? Walls. Buildings have walls, and so do many cities. They built giant walls around themselves to keep out enemies. The longest, widest wall of all is the Great Wall of China. It runs halfway across the whole country, and since it’s 16 to 20 feet wide, cars and people can travel on top of it. So our fan Scout B. asked, how long is the Great Wall? It zigzags through the mountains, because it connects pieces of wall built hundreds of years apart. If you straightened it out, it would stretch 3,889 miles. When you add in the rivers and other holes, it covers 5,500 miles! That’s more than twice as long as the U.S. How many houses could be built from that amount of wall? Let’s do the math!
Wee ones: How many walls does your room have? Do any rooms in your home have more than that?
Little kids: The Great Wall is 20 feet wide at the bottom and 16 feet wide at the top. Is it wider at the top or bottom? Bonus: The Great Wall is about 25 feet high in many places. If your ladder reaches 1 foot higher, how high does your ladder reach? If you can count up 1 from 5, try counting up 1 from 25!
Big kids: If a house is a 50-foot-wide square, how long are its 4 walls put together? Bonus: Let’s say you can make 20 full houses from 1 mile (5280 feet) of wall. How many houses can you make from 4,000 miles of Great Wall walls? (Hint if needed: What if you could make just 2 houses from each mile of wall?)
Wee ones: Different for everyone…most closed-in rooms have 4 walls, but if 1 side is open, it might have just 3. Or it might not be a rectangle!
Little kids: Wider at the bottom. Bonus: 26 feet.
Big kids: 200 feet. Bonus: 80,000 houses!
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.