2nd Grade – Robin Daugherty

Roman Numerals

I (1) – XII (12)

Objective: Students gain knowledge of the history of Roman Numerals and how to translate Roman Numerals I – XII to Arabic Numerals.

Roman Numerals

What are Roman Numerals?•Romans did not use numbers like we use…They used letters to represent their numbers.

•The Romans used a combination 7 letters to make all of their numbers!

•We use what is call Arabic numbers. We use the numbers 0-9 to make all of our numbers.

What is a Roman Numeral?

•The Following are the Roman Numerals that we are going to learn today:

I - 1 V – 5

X - 10

•For our number one, the Romans used a capital I.

•For our number five, the Romans used a capital V.

•For our number 10, the Romans used a capital X.

History of Roman Numerals

•The symbol "I" for 1 was derived from one finger. Five fingers held up indicated five of whatever was being counted.

•The "V" then was the hand outstretched vertically with the space between the thumb and first finger forming the "V".

History of Roman Numerals

•Another theory for "X" is that ten 1's were written in a row, and then crossed out with an "X" to simplify counting.

History of Roman Numerals

Then the "X" alone became a shorthand version of 10. Yet another idea is that "V" looks like the top half of "X", as 5 is half of 10, and other scholars think that "V" doubled with an upside-down "V" meant 5 times 2, or "X".

Rules for Roman Numerals

There are 3 basic rules for using and counting with Roman Numerals. We will go through the rules one-by-one and give examples for each rule.

First Rule

1. Add repeated numerals.

I – 1II – 2III - 3

Second Rule

2.Add when a lesser numeral follows a greater one.I = 1

V = 5

Which Numeral is Greater the I or the V?

Second Rule Cont…

2.Add when a lesser numeral follows a greater one.For the Number VI, the I

is less than the V so we add because we add when a lesser numeral follows a greater one. V + I = VI or 5+1=6.

Second Rule Cont…

2.Add when a lesser numeral follows a greater one.What is this number –

VII?7 because V = 5 and I = 1. So 5+1+1=7

Second Rule Cont…

2.Add when a lesser numeral follows a greater one.What is this number –

VIII?8 because V = 5 and I = 1. So 5+1+1+1=8

Third Rule

3. Subtract when a lesser numeral comes before a greater one.

I = 1V = 5

Which Numeral is lesser the I or the V?

Third Rule

3. Subtract when a lesser numeral comes before a greater one.

For the Roman Numeral IV, the I is less than the V, because I = 1 and V = 5. So, the number is V-I=IV or

5-1=4

Third Rule

3. Subtract when a lesser numeral comes before a greater one.

What is IX? X = 10 and I = 1.

The Answer is 9 because X – I=IX or 10-1=9.

Review of all Roman Numerals

I = 1 VIII = 8

II = 2 IX = 9

III = 3 X = 10

IV = 4 XI = 11

V = 5 XII = 12

VI = 6

VII= 7