# Pre-Algebra 2 - Roman Numerals: Sign-Value vs Positional Notation | Summary and Q&A

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July 29, 2011
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MyWhyU
Pre-Algebra 2 - Roman Numerals: Sign-Value vs Positional Notation

## TL;DR

The lecture explains the Roman number system and its differences from the modern positional number system.

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### Q: How did the Romans represent numbers 2 and 3?

The Romans represented 2 and 3 using two or three "I" symbols, respectively.

### Q: How were numbers 4 and 9 represented in the Roman system?

Numbers 4 and 9 were represented by combining the symbols for 5 or 10 (V and X) with an "I" symbol (e.g., IV for 4 and IX for 9).

### Q: Why did the Roman system not require a symbol for zero?

The Roman number system did not use positional notation, so a symbol for zero was not necessary as a column placeholder.

### Q: How does the modern positional number system differ from the Roman system?

Unlike the Roman system, the modern system uses the same symbol to represent different values based on its position in the number.

## Summary & Key Takeaways

• The lecture explores the Roman number system, which represents natural numbers using symbols I, V, X, L, C, D, and M.

• Symbols are combined to form numbers up to 3999, and a bar over symbols represents values 1000 times greater.

• Roman numerals are not based on positional notation like our modern number system; symbols have fixed values.