Monday, August 13, 2007

Crispy Green and head-scratching math

I was at my Aunt's house last night and happened to see a package of "Crispy Fruit." Intrigued, I snagged three small packets (two peach and one pineapple, which will become important later).

They were soooooooo amazing!


I'm a big dried fruit fan, but these tasted NOTHING like dried fruit. Freeze-dried, they truly were "crispy" and held a sweet almost fizzy taste on the surface, sort of like eating a fruit cracker coated by pop rocks. I simply cannot recommend them highly enough.

I found out the parent company is Crispy Green, which has this website. (You can also see where they sell them near you if you're interested.)


Okay, now to the Math.

The packages all look the same from a distance. When I sat down on my bed to watch TV I dropped one package, and I wasn't sure which one. I could see one peach, so that didn't help me. As I wrote earlier, I had one pineapple and two peach, which meant the odds of the package on the floor being pineapple was.... one in three.

Okay. I tried the peach. Of course I loved it and couldn't wait to eat more. I still didn't know which one had fallen. So, here's the question. What were the odds that the pineapple package WAS NOT the one that fell to the floor, and was still on the bed with me.

Two thirds.

That's right. There was a two in three chance that the package with me was the pineapple.

You may now furrow your brown in a vain attempt to understand the situation.

6 comments:

Avitable said...

I disagree with your math. You only had two unknowns, which means that there was a 50% chance that the one on the bed was pineapple.

Once the peach that you ate became a known, it was removed from the equation.

Hyperion said...

I'm delighted to see people disagree, and I admit that 50% is the intuitive answer, but the correct odds are actually 2/3 that the pineapple will be on the bed.

It's weird, but it's true.

Anonymous said...

It seems like a timing thing. You know that one of the packages that did not fall was a peach package, but you know this AFTER THE EVENT OCCURRED. This after the fact knowledge does not affect what the probability was when the "choice" was made. When the package fell, it was still 1 package out of 3 possible packages.

Hyperion said...

Bear has hit the nail on the head. Just because one of the choices has been removed does not change the original probability. As weird as it sounds, there is still a 2/3 chance for the pineapple to be on the bed with me. (And doesn't THAT sound like my last date.)

Avitable said...

I still disagree.

When the package dropped, there was a 1:3 chance that the one on the floor was pineapple.

At the time the package dropped, yes, this meant that the chance was 2:3 that the one on the bed was pineapple.

But the way you wrote it, you were re-determining the probability after having eaten a package, which meant that there were only two unknowns at that time. If you had asked what the original probability was, you're right. But you weren't.

Odds are drawn and re-drawn at every given second using all available knowledge and information, so it's just a matter of semantics of when you were calculating the odds.

Anonymous said...

MY question is - why the hell don't you just LOOK at the freaking packages on the bed?!?!