Great article. Just one small tip: instead of using the BigDecimal("123.45") notation, I much prefer typing 123.45.to_d.

Anywhere you used Floats, you can just replace them with BigDecimals. They work just the same. Some people get scared by them because they are always printed in scientific notation in the console, but you can just call `.to_s` on them to see them in a regular format:

123.45.to_d => 0.12345e3

123.45.to_s => "123.45"

So don't get worried about the display. The behave exactly the same as a float, you can sum, multiply, and so on, and then you call .to_s when it's time to display it.

Also any BigDecimal#round will give you an integer (just like .to_i will), but you can also call Bigdecimal#round(2) to round to, for instance, 2 decimal places.

Also, if you are coding anything related to currencies, I strongly suggest you always use integers to store the amounts in cents. And when you need to divide it for calculations, just call `.to_d`, do your math, and then `.round` at the end, so you discard the fractions of cents. It works wonders, and the math will add up just like in Excel :)