Saturday, November 15, 2008


Consider the thickness of a piece of standard binder paper - pretty thin - about 3/1000 (or 0.003) of an inch thick. Imagine tearing it in half and stacking up the two halves; now it's twice as thick but still pretty thin. Now tear it in half a second time and stack up the four pieces - then imagine tearing and stacking again and again until you have done so 50 times. IF you could do this 50 times how thick would the stack be?

This is the extra credit my students are working on this weekend.

In class I had them make a guess; their guesses ranged from 1 inch to 1 foot. They were being so conservative that I said, "I submit to you that it will be 5 million miles thick." After getting looks of shock I said, "Your extra credit assignment is to prove me wrong - or prove me right. It's due Monday."

What do you think the answer is? Was I just lying to get them interested? Am I right or wrong? If I'm wrong, by how much?


Anonymous said...

I am going with the professor on this on. I think it is more like 17 million miles myself. I remember one math prof. of mine asking the class if they would like $1 million dollars today or 1 penny today, two the next and so on doubling the amount each day for 30 days. The pennies added up to over $10 million.

Uncle D from Chicago.

Heidi said...

Ahh . . . upping the ante!

So perhaps I am wrong but in a different direction than my students might think??

Hmm . . .

Anonymous said...

Wow, how cool is that to wrap your mind around? I have no idea the answer...but Uncle D's money problem is also very clever, especially since some people are put off by saving, for they have only a small amount, but even pennies add up! Paula

Dwight said...

53,309,654.7 miles according to my son the math wiz. Dad gave me your blog address back when David had his stroke but I was in Colombia at the time adopting our youngest son so it got lost in my archived mail. Just rediscovered it this week when I was moving all my mail to a new account because we all moved out to NW Iowa to pursue new careers. Aside from running into Jeff and his wife a few times in and around our old home in Holland MI it is fun to catch up on the lives of old friends.
Dwight VanTol

Heidi said...

Wow! How did you happen to come across this post from so long ago?

Your math-wiz son is correct!

It's just numbers, I think, until you realize the moon is only one-quarter of ONE million miles from earth, which means you could take this stack and separate it into 213 smaller stacks all of which would reach the moon! All that from folding one piece of paper 50 times!

Ah - the power of exponents!

Good to hear from you! Thanks for checking in and for commenting - and kudos to your son!