Monday, July 18, 2011

Answer to our Friday Fermi Problem: Eating the Iron Skillet


Here's our answer to the Fermi problem we posted last Friday . . .

The typical recommended daily allowance of iron is about 15 milligrams/day.

A 12 inch skillet weighs about 3 kilograms.

So a single skillet could provide a single person with 3000/.015=200,000 daily doses of iron before the pan is entirely consumed.

But a pan isn't very useful once enough of it is so worn away that it won't hold your eggs any more, so let's assume that you can only eat up about 1/5 of the pan before it's no good.

That means you can get your daily iron fix from a single skillet for 40,000 days, or 109 years if you use it every day.

There's a good chance, however, that the skillet is not just for you, but for a group of people like a family. The typical family has about 4 members. If they all get their daily iron from the same skillet, the pan would last about 109/4 = 27.25 years.

At least one cooking site claims that iron skillets will last a lifetime. If you define a lifetime as 75 years, our estimate suggests that they may be stretching the truth a bit. On the other hand, it's unlikely that anyone is going to use the same pan to cook family meals every day.

In other words, an iron skillet almost certainly will last a lifetime, but probably not much more.

3 comments:

  1. You are basing how long it will last on the RDA. Who says that we eat our RDA in iron when we cook with a skillet? Obviously we don't. So an iron skillet will probably last a lifetime and much more.

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  2. I'm basing the calculation on Vanna's claim that food cooked in a skillet is a good source of iron. If it doesn't provide something close to the RDA, then it's not a good source of iron. Therefore, if we accept Vanna's premise, we have to estimate that it provides roughly the RDA of iron.

    Of course, she could be wrong.

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  3. Heh ... one suspects that the necessary steady diet of fried food would cause the skillet user to expire long before the skillet ...

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