Fun math facts

[General Kenobi (ret.)]

Let's say you were giving a talk to a bunch of 8th graders about math, and you wanted to give them some fun math facts, like 57% of all CDs sold in America have Brittney Spears's picture on them (OK, maybe that's more of a sad fact, or would be if it were true)--anything kind of interesting with a number in it, basically.

What would you say (with source documentation, if possible)?

[Pseudolus]

You could do the "pennies on a checkerboard" thing. You know, put one penny on the first square, double that on the second, double that on the third.... eventually you have the national debt, or something. Power of exponentials.

Try folding a newspaper 8 times.

[jets fan]

If you have at least 50 people in the classroom, I'll guarantee you that at least 2 of them have the same birthday (it's over a 97% chance).

[Pillow]

I have a nerdy math joke for an opener.

Draw three trees on the board. Ask them how many you have on the board. Obvious answer is 3. Wrong...it's tree + tree + tree = 9. (say these out loud if you aren't getting it.)

Now, a wind storm comes back and the trees are now covered with dust (make some specs on the tree design on the board to represent dust). Ask them how many you have now. (Most will now be scared to answer.) You say, there are 99...dirty tree + dirty tree + dirty tree = 99.

Now, overhead fly three birds. Each of them takes a dump on their flight over the trees and lands on each tree. (Make a big glob on the tree to represent the bird's business.) Ask them how many you have now. You answer 100. Dirty tree and a turd + dirty tree and a turd + dirty tree and turd = 100.

You might be kicked out of the room and not allowed to come back after telling such a "joke", but nothing beats nerd humor.

[Polly Nomial]

Suppose you had an elastic rope that circled the earth. And then suppose you got the people of the world to lift the rope one foot off the ground (or water). How much longer would the rope have to stretch?

[Traci]

I like to see if they're paying attention: I write 64 over 16 on the board, then say that the answer is 4 because the 6's cancel each other out - and see how long it takes someone to speak up.

It's a nice lead-in to the importance of getting the methodology correct - not just the answer.


There's also the ever-popular 111,111,111 times 111,111,111 equals

12,345,678,987,654,321

[Ron Weasley]

One idea that I was enthralled with at that age is very similar to Pseudo's "pennies on a checkerboard." The idea was: If you had a job mowing grass every day for a month, would you prefer to be paid $100 per day or $0.01 on the first day, $0.02 on the second, $0.04 on the third and so on.

Variation's on Xeno's paradox, such as stepping of a cliff and falling 1/2 way, and then 1/2 again as much, and then 1/2 again as . . . . Will you ever reach the bottom? Prove it.

Using real world data, you can hit the Treasury Site for the National Debt Figures and the Census Bureau for population figures, let them do the division to see what is owed per person. This can lead to their discussion of the possibility of paying it off, who should pay how much, the ages and abilities of individuals (given toddlers and disabled adults) within the population to contribute to paying down the debt, etc.

Hope that helps.

RW

[General Kenobi (ret.)]

Great ideas! Thanks!

[Darth Tater]

If they are all in 8th grade, that makes them all about 13 -- You could tell them they are all in their prime and let them in on the fact that they can only look forward to about 20 or so more of those or let them know that they won't be in their prime again until they are seniors (or 17 years old).


That may just put them right to sleep then you and the teacher can swap dirty jokes!!!