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Roman Numerals on a Prescription
Consider the following: The main
differences between Roman and Arabic numerals are that Roman numerals lack a symbol for zero, and that numeral
placement within a number can sometimes indicate subtraction rather than addition. In order to write, read,
and fill out prescriptions the healthcare professional must understand Roman numerals. Roman numerals are
commonly used in pharmacology, especially when it comes to the Sig on prescriptions.
For example: Take three tablets three times a day is often written as III tabs t.i.d.
I
The easiest way to write a roman number is to mark that many lines down - they
look like little i's. Thus I means 1,
II means 2, III means 3. However, four strokes seemed like too
many....
V
So the Romans moved on to the symbol for 5 - V. PlacingI in
front of the V — or placing any smaller
number in front of any larger number — indicates subtraction. So I before V as inIV means 4. After V comes a series of additions - VI means 6, VII means 7, VIII means 8.
X
X means 10. But what about 9? Same thing. IX means to subtract I from X, leaving 9. Numbers in
the teens, twenties and thirties follow the same rule as the first set, only with X's
indicating the number of tens. So XXXI is
31, and XXIV is 24.
L
L means 50. Based on what you've learned, I bet you can figure out what 40 is.
You guessed it right, that's XL, since 10
subtracted from 50 is 40. And thus 60, 70, and 80 are LX, LXX and LXXX.
C
C stands for centum, the Latin word for
100. A century lasts 100 years. We still use this word
in "cent" (one hundredth of a dollar) and centimeter (one hundredth of a meter). The
subtraction rule means 90 is written as XC. Like the X's and L's, the C's are tacked on to
the beginning of numbers to indicate how many hundreds there are: CCCLXIX is 369.
D
D stands for 500. As you can probably guess by this time, CD means 400. So CDXLVIII is 448. (See why we switched systems?)
M
M is 1,000. You see a lot of Ms because Roman numerals are used a lot to
indicate dates. For instance, if you know someone that was born in 1998 then that year is
written as MCMXCVIII.
V
Larger numbers were indicated by putting a horizontal line over them, which meant to multiply the number by 1,000. Hence the
V on the has a line over the top,
which means 5,000. This usage is no longer current, because the largest numbers usually
expressed in the Roman system are dates, as discussed above.
* adapted from Nova Roma on Roman Numerals under Fair Use
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Consider the following:
For example:
them, which meant to multiply the number by 1,000. Hence the
V on the has a line over the top,
which means 5,000. This usage is no longer current, because the largest numbers usually
expressed in the Roman system are dates, as discussed above.
Take the Roman Numeral Challenge at Fact Monster
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