1. Numeration Systems Numerals did not start out as 1, 2, 3, … The first numeration systems were often 1, 2, many. 0 wasn’t needed. More complex number systems arose out of need.

2. Numeration Systems Tally systems: |||| at a time. Egyptian--probably earliest known Babylonian--only two symbols Roman--most widespread, all over Europe from the Roman Empire Mayan--only three symbols Hindu-Arabic--what we use today

3. A brief look at Egyptian Numerals Used at about the same time as Babylonian Numbers--many similarities More symbols: 110 100 1000 10,000 More symbols for 100,000 and 1,000,000

4. Egyptian Numerals 300 + 10 = 310 (Notice no ones) 20,000 + 300 + 4 = 20304

5. Egyptian Numerals 300 + 10 = 310 (Notice no ones) 20,000 + 300 + 4 = 20304

6. A brief look at Babylonian Numerals Initially, no zero. Later developed: Two symbols only:  = 1; = 10. Additive when written from greatest to least:    = 10+10+1+1+1 Use 60 as a base--there is a break after 60.     means 60+60+60+10+1

7. Babylonian Numerals    = 1 ____ + 11 60 + 21 = 1 60 60 + 11 60 + 21 = 3600 + 660 + 21 = 4281

8. A brief look at Mayan Numerals Used the concept of zero, but only for place holders Used three symbols:--- 150 Wrote their numbers vertically:is 3 + 5 = 8, --- is 5 + 5 = 10

9. Mayan Numerals New place value… left a vertical gap. is one 20, and 0 ones = 20. is two ___ + 6

10. A brief look at Roman Numerals No zero. Symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000 If the Roman Numerals are in order from greatest to least, then add: VII = 5 + 1 + 1 = 7; XVI = 10 + 5 + 1 = 16

11. Roman Numerals I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. If the Roman Numerals are NOT in order from greatest to least, then subtract where the order is wrong. IV = 5 - 1 = 4; IX = 10 - 1; XCII = 100 - 10 + 1 + 1 = 92

12. Exploration 2.8 Exploration 2.8--We will not do this entire thing--it is too long! But we will do parts. Today, we will begin with manipulatives.

13. Alphabitia Read the introduction. Use the “artifacts”. UnitLong Flat

14. Your job: See if you can create a numeration system, like the ones we have just seen. Make notes, and be ready to explain it to others who are not part of this tribe. It should be logical, and be able to be continued past Z. Keep the materials for Monday.

15. Alphabitia Numeration System Proposals What did you come up with in your group? What are the pros and cons of your group’s system and the other groups’ systems?

16. What makes an efficient numeration system?

17. Alphabitia A numbering system is only powerful if it can be reliably continued. Ex: 7, 8, 9, … what comes next? Ex: 38, 39, … what comes next? Ex: 1488, 1489, … what comes next?

18. The Numeration System we use today: The Hindu-Arabic System Zero is used to represent nothing and as a place holder. Base 10Why? Any number can be represented using only 10 symbols. Easy to determine what number comes next or what number came before. Operations are relatively easy to carry out.

19. In Base 10… Digits used are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 We can put the digit 9 in the units place. Can we put the next number (ten) in the units place? Only one digit per place Placement of digits is important! 341 ≠ 143. Can you explain why not?

20. Exploration 2.9 Different Bases

21. In another base… We need a 0, and some other digits So, in base 10, we had 0 plus 9 digits What will the digits be in base 9? What will the digits be in base 3? Which base was involved in alphabitia?

22. So, let’s count in base 6 Digits allowed: 0, 1, 2, 3, 4, 5 There is no such thing as 6 When we read a number such as 213 6, we don’t typically say “two hundred thirteen.” We say instead “two, one, three, base 6.”

23. Count! In base 6 1, 2, 3, 4, 5, … 10, 11, 12, 13, 14, 15, … 20, 21, 22, 23, 24, 25, … 30, 31, 32, 33, 34, 35, … 40, 41, 42, 43, 44, 45, … 100, … 100, 101, 102, 103, 104, 105, … 110

24. Compare base 6 to base 10 Digits 0,1,2,3,4,5,6,7,8,9 New place value after 9 in a given place Each place is 10 times as valuable as the one to the right 243 = 2 (10 10) + 4 10 + 3 1 Digits 0 - 5 New place value after 5 in a given place Each place is 6 times as valuable as the one to the right. 243 base 6 = 2 (6 6) + 4 6 + 3 1 or 99 in base 10

25. Compare Base 6 to Base 10 312 = 3 100 + 1 10 + 2 1 312 base 6 = 3 36 + 1 6 + 2 1 = 116 in base 10

26. How to change from Base 10 to Base 6? Suppose your number is 325 in base 10. We need to know what our place values will look like. _____ _____ 666 66 6 1 Now, 666 = 216. 216 = 1000 in base 6.

27. Base 10 to Base 6 ___1__ _____ _____ _____ 666 66 6 1 Now, 325 - 216 = 109. Since 109 is less than 216, we move to the next smaller place value: 6 6 = 36. 109 - 36 = 73. Since 73 is greater than 36, we stay with the same place value.

28. Base 10 to Base 6 __1___ ___3__ _____ _____ 666 66 6 1 We had 109: 109 - 36 - 36 - 36 = 1. We subtracted 36 three times, so 3 goes in the 36ths place. We have 1 left. 1 is less than 6, so there are no 6s. Just a 1 in the units place.

29. Base 10 to Base 6 __1___ ___3__ __0___ __1___ 666 66 6 1 Check: 1 216 + 3 36 + 1 1 = 325 So 325 = 1301 6

30. Count! In base 16 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1a, 1b, 1c, 1d, 1e, 1f, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 2a, 2b, 2c, 2d, 2e, 2f

31. Homework for Friday Exploration 2.9: Part 1: for Base 6, 2, and 16, do #2; Part 3: #2, 3, Part 4: #1, 2, 4. For the base 16 section, change all the base 12 to base 16 (typo) Read Textbook pp. 109-118 Do Textbook Problems pp. 120-121: 15b,c, 16b,d, 17a,i, 18b,f, 19, 29