# How Many Houses?

Our friend Alan D-S. asked us a great question: how many buildings are there in the world? And he means everything from teepees to skyscrapers. Well, no one has made a nice neat list of buildings for the whole world. Some countries count them up, while others don’t; even inside the countries who do, it’s usually cities and towns who keep track. But we can use math to make a good guess. The more people stuffed into a town, the more buildings they need – except when it gets so high that lots of people live in one tall building. Out on farmland there might be just 1 building every square mile, but in New York City, one street block 1/20 of a mile wide might have 20 buildings crammed into it. If we run the numbers, we can find a guess at least for the U.S. Just remember that might not work everywhere: we’re pretty sure Antarctica has more penguins than buildings!

Wee ones: Look at your home from the outside. Is it taller than it is wide, or wider than its height?

Little kids: How many people live in the building you call home? Talk about it with a grown-up!  Bonus: If a building has 7 floors with 10 people living on each, how many people live there?

Big kids: If a square city block has 5 buildings on each edge, how many buildings are on the whole block? (Remember, the corner buildings each sit on 2 sides!)  Bonus: If 100 people live in each, how many people is that?

The sky’s the limit: The U.S. covers about 3,800,000 square miles, and about 1/3 of it has no people. If 1,000,000 have 1 building each square mile, another 1,000,000 have 4 buildings each, and the last 500,000 average 30 buildings each, how many buildings do we have? See if you can remember all the parts!

Answers:
Wee ones: Different for everyone…an apartment building is taller than wide, but a house (like a ranch style) could be wider than tall.

Little kids: Different again…count just your family for a single-family home, but an apartment building will have many more.  Bonus: 70 people.

Big kids: 16 buildings, since each side adds 4 new ones. Another take: 5 on a side means 2 corner buildings and 3 middle ones; you have 4 of those sets of 3 plus the 4 corners.  Bonus: 1,600 people.

The sky’s the limit: 20 million buildings (1 + 4 + 15). That could be low, as one site says we have more than 5 million office buildings only. Also, New York City has about 1,000,000 buildings for 8 million people; the U.S. has at least 40 times as many people, which would give us 40 million buildings for all of them.

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