Simple Arithmetic
So far, we have all the makings of a simple calculator. (Calculators always use floats, so if you want your computer to act just like a calculator, you should also use floats.) You type numbers using the digit keys (either at the top of your keyboard or on the numeric keypad). For decimal points, you use the period (or full-stop, normally close to the M key on the bottom row or over on the numeric keypad). Don’t, however, type commas into your numbers. If you enter 1,000,000, you’ll just confuse Ruby.
For addition and subtraction, we use + and -, as we saw. For multiplication, we use *, and for division we use /. Most keyboards have these keys in the numeric keypad on the far-right side, but you can also use Shift8 and
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