So the other day I needed to print something out. At my library, to save money on ink and paper, the school “requires” you to pay 10¢ per page of black and white print and 25¢ per page of color print. However, normally I don’t bring money to school, and I had to print my paragraph for LA class. So I looked at the one thing i had in my backpack: a paper clip. Why not pay with these? I asked myself. So let’s find out.

A quick Wikipedia search reveals that most paper clips are made out of steel wire or plastic. my paper clip was shiny and easily bendable, so it’s probably the steel wire. A Google search finds a website called “worldsteelprices.com”, so i could probably find the price of steel there. For March-13, steel costs about $720 / tonne. Use of the school’s digital scale tells me the paper clip weighs 5 grams. So i need to convert 720 $/tonne to $/gram. Google again tells me that 1 tonne = 1000000 grams, so using dimensional analysis (or the factor label method), 720 $/tonne = 7.2* 10^-4 $/gram, or 0.00072 $/gram. Mulitply by five to get 0.0036 $/5 grams.

So my 5-gram paper clip is worth about 0.36 ¢. Thirty-six tenths of a cent. Well i’m not paying for my copies with that, but there are a whole bunch of paper clips in my backpack. How many do i need to pay for my print?

1 paper clip = 5 grams = 0.0036 $ of steel wire.

-> 28 paper clips = 140 grams ≈ 0.10 $ of steel wire.

So I need 28 paper clips to pay for 10¢ of black-and-white copies. But I also need to print out my lab report for science, which is 14 pages long, also black and white, and two more pages need to be color graphs. Color pages are 25¢, so I’ll need 139 paper clips for ≈ 50¢. My 14 black and white copies mean that I’ll need 392 paper clips, and my two color graphs will cost me 278 paper clips.

Hopefully the payment box can handle 698 paper clips.