How Medieval Taxes Shaped Fractions, Decimals & Percentages

Imagine you’re splitting a pizza, reading a sale sign or checking your phone’s battery life—and there they are: fractions, decimals and percentages, all around us. These three ways of breaking down numbers seem straightforward today, but did you know their history involves ancient scribes, Renaissance mathematicians and medieval tax collectors? Let’s dive into this trio of number systems, see how they’re connected, and find out why they still matter in everyday life.

Where did this come from?

Long before digital calculators, Egyptian scribes carved unit fractions (fractions with 1 as the numerator) into papyrus around 1800 BCE—sums of fractions like 1/2 + 1/6 + 1/12 made up more complicated values. Fast forward to 1585: Flemish engineer Simon Stevin published De Thiende (The Tenth), pushing decimal fractions in Europe so people could ditch awkward unit sums. Meanwhile, percentage signs crept into ledgers in medieval Venice, helping tax collectors and merchants calculate “per centum” (meaning “by the hundred”) on goods and interest.

Where you’ll see this in real life

• Shopping sales: 25% off or buy one get one 50% off? That’s percentages at work. • Bank interest & loans: Banks quote rates as percentages, then use decimals under the hood to calculate how much you’ll pay or earn. • Cooking & recipes: Converting cups to grams (fractions) or scaling a recipe up by 150% (decimals) keeps your cake perfect. • Sports stats: Batting averages in baseball or win rates in football use decimals and percentages to compare players and teams.

A common misconception

You might think decimals are just “nicer” fractions, but rounding can lead you astray. For example, if you round .333… to .33 then multiply, your answer might be off by more than you expect—those tiny leftover bits add up! The same goes for percentages: if each category in a survey is rounded, the total could end up as 99% or 101%, confusing your results. So next time you see a rounded decimal or percentage, remember there’s a little history—and a little error—behind it.