Unit 1, Part 1: Using Roman Numerals

1.1 Using Roman Numerals 

Learning objectives:

1. Define the key terms that relate to Roman numerals
2. Demonstrate how to convert Arabic numbers into Roman numerals and vice versa

 Key Terms:

• Roman Numerals
• Hindu-Arabic Numerals

In healthcare you may encounter Roman numerals used in documentation, written prescriptions, drug scheduling, laboratory testing or general numbering.

The Hindu-Arabic number system, or simply Arabic, is the numbering system most commonly used in the United States. It consists of numbers 0 through 9, all other numbers are a combination of these numbers. We place value on the numbers according to the placement of the number. Number placement and place value will be discussed later in this unit.

The Hindu-Arabic system was developed around 600 A.D. in India by the Hindus and was brought to the western world by the Arabs about 100 years later.

Roman numerals are letters written in both upper and lower case. (See table 1.1A.) Letters are placed in a specific order to create a value. (A reference table is listed at the end of this sections, table 1.1B)

The Roman Numeral system was developed over 3,000 years ago by the people of ancient Rome. The system is thought to have developed from tick marks on rocks or the ground.

Table 1.1A

Roman Numeral (upper case)	Roman Numeral (Lower case)	Arabic Numeral
	ss	1/2
I	i	1
V	v	5
X	x	10
L	l	50
C	c	100
D	d	500
M	m	1,000

 

Converting Arabic numbers to Roman Numerals

I. Roman numerals are arranged and combined in a specific order to represent numbers. Numerals (their values) are added together when written in groups, so XX = 20 (because 10+10 = 20). You cannot put more than three of the same numerals together. You can write III for three, but you can't use IIII. Instead, four is indicated with IV. To avoid using three of the same numerals, you will use the next value up and subtract.

Example: IX is equal to 9 because you subtract 1 from 10 (I - X). 

Example: II is equal to 2 because you add 1 to 1 (I + I)

Example: VI is equal to 6 because you add 5 to 1 (V + I)

Practice 1.1A

Directions: Using the examples above, convert the Hindu-Arabic numbers to Roman numerals and add or subtract. Show your work just like the examples. Complete the following practice and submit all practice assignments for this section below.

1. Write Roman Numeral for 3
2. Write Roman Numeral for 4
3. Write Roman Numeral for 8
4. Write Roman Numeral for 20
5. Write Roman Numeral for 19

II. Convert Arabic numeral to Roman numerals by selecting the largest Roman numeral that equals a portion of the number.

Example: Convert Arabic number 129 to Roman numerals.

$\longrightarrow$Find the largest Roman numeral; C = 100

$\longrightarrow$Subtract this number from the total; 100 - 129 = 29

$\longrightarrow$Find the largest portion of this number; X = 10

Since X is the largest Roman numeral you can use, decide how many X's you need by dividing 10 into 29. The 10 will go into 29 twice; place two X's to the right of C.

$\longrightarrow$CXX = 120

$\longrightarrow$Subtract this from the total number; 129 - 120 = 9

Since we cannot use more than 3 Roman numerals together, we cannot write 9 as VIIII. We need to use I - X, or IX for 9.

129 = CXXIX

Example: Convert Arabic number 98 to Roman numerals.

$\longrightarrow$Find the largest Roman numeral; Since 98 is closer to 100 (C) than it is to 50 (L), we know that we will be subtracting Roman numerals to create this number.

$\longrightarrow$X - C = 90 so we write XC for 90.

$\longrightarrow$Subtract this number from the total; 90 - 98 = 8

$\longrightarrow$Find the largest portion of this number; 5 = V

$\longrightarrow$XCV = 95

Subtract this number from the total; 95 - 98 = 3, 3 = III

98 = XCVIII

Practice 1.1B

Directions: Convert the following Arabic numerals to Roman numerals. Show your work just like the examples above. Complete the following practice and submit all practice assignments for this section below.

1. 145
2. 3,420
3. 333
4. 453
5. 1,394

Converting Roman Numerals to Arabic numbers

I. To convert Roman numerals to Hindu-Arabic numbers, convert the Roman numerals to Arabic and add or subtract. 

Example: XXVII

$\longrightarrow$X  + X +V +I +I = XXVII

$\longrightarrow$10+10+5+1+1 =  27

Example: MCMXXXIV

$\longrightarrow$M        +       (M - C)     +  X  +  X   + X   +  (I - V) = MCMXXXIV

$\longrightarrow$1,000 + (1,000 - 100) + 10 + 10 + 10 +  (5 - 1)

$\longrightarrow$1,000 +          900        + 10 + 10 + 10 +     4    =   1,934

Practice 1.1C

Directions: Convert the following Roman numerals to Arabic numbers. Show your work just like the examples above. Complete the following practice and submit all practice assignments for this section below.

1. XXVI
2. DCI
3. MM
   
4. MCMLXV
5. DCLX
6. CXXXVIII
7. XXIV
8. DCLI
9. MCL
10. MMMDXL

Submit all practice assignments here.

 

Table 1.1B

						M=1000			D = 500
I	1		XXXII	32		LXIII	63		XCIV	94
II	2		XXXIII	33		LXIV	64		XCV	95
III	3		XXXIV	34		LXV	65		XCVI	96
IV	4		XXXV	35		LXVI	66		XCVII	97
V	5		XXXVI	36		LXVII	67		XCVIII	98
VI	6		XXXVII	37		LXVIII	68		XCIX	99
VII	7		XXXVIII	38		LXIX	69		C	100
VIII	8		XXXIX	39		LXX	70
IX	9		XL	40		LXXI	71
X	10		XLI	41		LXXII	72		DI	501
XI	11		XLII	42		LXXIII	73		DL	550
XII	12		XLIII	43		LXXIV	74		DXXX	530
XIII	13		XLIV	44		LXXV	75		DCCVII	707
XIV	14		XLV	45		LXXVI	76		DCCCXC	890
XV	15		XLVI	46		LXXVII	77		MD	1500
XVI	16		XLVII	47		LXXVIII	78		MDCCC	1800
XVII	17		XLVIII	48		LXXIX	79		CM	900
XVIII	18		XLIX	49		LXXX	80
XIX	19		L	50		LXXXI	81
XX	20		LI	51		LXXXII	82
XXI	21		LII	52		LXXXIII	83
XXII	22		LIII	53		LXXXIV	84
XXIII	23		LIV	54		LXXXV	85
XXIV	24		LV	55		LXXXVI	86
XXV	25		LVI	56		LXXXVII	87
XXVI	26		LVII	57		LXXXVIII	88
XXVII	27		LVIII	58		LXXXIX	89
XXVIII	28		LIX	59		XC	90
XXIX	29		LX	60		XCI	91
XXX	30		LXI	61		XCII	92
XXXI	31		LXII	62		XCIII	93