So, you think you're smart, huh? Well, here's a JavaScript that will test that theory. Just grab and paste, it does the math for you.
Please note: This script is being offered in simple text format. When you click to Grab the Script, the text should display. Internet Explorer and AOL users may get a blank page or the script may run and produce the effect. If this happens, choose SAVE AS from the FILE menu and save the blank or compiled page.