## Monday, November 21, 2011

### Add and Subtract with Roman Numerals

My son’s class is working on telling time. His homework assignment one night was to find and count the number of clocks in our home. He also had to draw one of them. Of course, he chose the clock with roman numerals. This got me thinking. Maybe he’d enjoy learning about roman numerals. And thus, this activity was born.

Our library had an amazing book that was both fun to read and extremely helpful (I never learned roman numerals so I was totally clueless).

From David Adler’s book, I made a cheat sheet for my son translating the values of each numeral.
I = 1
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1,000

Then, I made a game board and playing cards. I laminated the board to use over and over with a dry-erase marker.

 Download a PDF of the game board, playing cards, and cheat sheet here.

The game board has a reminder about three important rules:
When the same number is repeated one after the other, the numbers are added.
When a larger number is followed by a smaller number, the numbers are added.
When a smaller number is followed by a larger number, the smaller number is subtracted from the larger.

Since my son is only in first grade, we did not use the “D” (500) and “M” (1,000) cards I made; I’ll save those for when he’s ready to add and subtract larger numbers. After reading the first half of Fun with Roman Numerals (the more you read, the more complex the combination of numerals becomes), I placed three cards on the game board and asked my son to write their values underneath with a fine-tip dry-erase marker.

To start, I placed the cards in descending order by value so no roman numeral was followed by one that had a higher value. Doing this meant that the numbers would always be added. I gave my son a 1-100 numbers grid for help when he needed it. Once he had the answer, he wrote it at the bottom of the game board. We cleared the dry-erase marks on the board with a paper towel.

Gradually I added different cards, progressively making the addition harder. Eventually, I placed a numeral with a higher value in the middle or at the end, so my son would have some subtraction practice. This tripped him up at first, but eventually he caught on and began thinking about whether greater than/less than numerals should be added or subtracted.

Teaching a first-grader roman numerals was tough but my son loved it. Now he can not only read our kitchen clock, but also will be able to tell me what number Super Bowl it is this year!

1. I LOVE this!!! You are an amazing mom/teacher!

Dana

2. What a great activity! I think any young kid would enjoy learning how to "decode" roman numerals!

3. We didn't tackle roman numerals yet except of talking about them briefly. This game is super fun, but I don't think that VVI is a real roman number. It would be written XI.

4. As Adler points out in his book, you can write any number in a variety of ways with Roman Numerals. That's what makes them perfect for this math activity - there's oodles of combinations! :)

5. Thank you for sharing on Hey Mom, Look What I Did at Adventures In Mommy Land...hope to see you again soon!!

6. This looks like a wonderful book!

7. Great stuff. Thank you. God Bless

8. that's great :D
is that roman numerals same like egyptian ?
like below source ?