Which Weighs More? A Pound Of Feathers Or A Pound Of Gold?

 

For the weekend warm-up, I looked up the number of feathers in a pound and came across a very interesting answer to the question -"Which weighs more, feathers or gold?"  The normal person will usually answer it with either "Don't they weigh the same?"  or "The gold of course because it obviously weighs more. 

Most people don't realize that the two items are weighed using two different systems.  Feathers are weighed using the "avoirdupois" system which uses 16 ounces per pound where as gold is weighed in the troy system which only has 12 ounces per pound.

Furthermore, the avoirdupois system is used to weigh things like food, people, mail, and equipment while gold, silver, and other precious metals are weighed with the troy system.  So if both the feathers and gold are weighed in the troy system, something strange happens.  The feathers weigh more than the gold.  This happens because one avoirdupois ounce is equal to about 28.1 grams while one troy ounce is equal to 31.1 grams. So a 16 ounce pound of feathers weighs around 453 grams while the 12 ounce pound of gold weighs around 373 grams.  

The whole troy system got it's start in the French town of Troyes and was based on pennyweights and grains of wheat or barley.  Yes, grains of wheat but more on that later.  First a troy ounce has an assigned equivalence of 20 pennyweights and a pennyweight was defined as the weight of a silver penny in England.  Now back to grains.  The grain of wheat or barley is the basis of both the weights in the troy and the avoirdupois systems.  

If you look at the grains as the basis of both troy and avoirdupois systems, you'll find one carat is equal to 4 grains, a troy ounce is defined as 24 grains and a gram is 15.432 grains. Now the thing about the grain measurement is that the troy systems is said to have been based on barley grins while the wheat grain was used as the standard of weight.  Apparently three barley grains equaled four wheat grains.

The question of "Which weighs more? A pound of feathers or a pound of gold opened up the possibility of having students learn more about avoirdupois and troy systems, their differences, and what they are used to weight.  In addition, it opens the door to include some history into the math class and it also can lead the the question of "Is it fair to compare these two items in the way it was done?".  Who knows you might get some interesting opinions from your students.

I hope you found this as interesting as I did.  Let me know what you think, I'd love to hear. Have a great day and enjoy your weekend.