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Numbers

• General Rules
  
• Special Cases
  Physical Quantities
  Dates
  Time of Day
  Money
  Decimals and Percentages
  Organizations and Governmental Units
  
• Forms and Uses of Numbers
  
• Roman Numerals
  
• The Metric System
  Base and Supplementary Units
  Combination Units
  Prefixes

GENERAL RULES

There is no simple, consistent formula for deciding whether to use figures or words for numbers in textual matter. The decision often hinges on whether you are using a precise number or are using a number in a nonprecise way. The nature of the writing must be considered; figures are generally used less often in ordinary prose than they are in technical or scientific writing. Ease of comprehension, practicality, and typographic appearance also can affect the decision. Consistency, of course, should be uppermost in mind. The following rules deal with the most common instances in which you must choose between a figure and a word.

1. In nonscientific writing, spell out exact numbers of less than 10; use figures for numbers of 10 or more. Follow this rule for both ordinal and cardinal numbers.
   
   

   	four years
   	12 courses
   	third-quarter freshman
   	21st precinct

   
   
2. Treat consistently throughout a sentence or paragraph all numbers refering to the same category. If the largest number is 10 or more, use figures for all the numbers.
   
   

   	Of 117 campus newsletters, 4 are issued weekly, 35 are issued monthly, 72 are issued quarterly, and 6 are issued annually.
   	During the past four months, the two newest recruits to the campus police force have issued 49 parking tickets, 2 of which were for double-parking.

   
   
3. When it is the first word of a sentence, spell out a number that would normally be written as a figure. If possible, rephrase a sentence to avoid beginning with a number.
   
   

   Thirty-nine percent of the students attending day school voted. Of the students attending day school, 39 percent voted.

   
   
4. Treat related numbers appearing at the beginning of a sentence alike if they are separated by no more than three words. Otherwise, spelling out a number as the first word of a sentence does not affect other numbers in the sentence.
   
   

   	Thirty or forty undergraduates normally attend her lectures.
   	One hundred and twenty faculty members and graduate students, 70 from the humanities and 50 from the health sciences, signed the petition.

   
   
5. A colon preceding figures does not affect their use.
   
   

   	The tally was as follows: 12 voted for the amendment, 4 voted against it.
   	The tally was as follows: three voted for the amendment, six voted against it.

   
   
6. Spell out indefinite numerical expressions. (A precise number preceded by a word like about, approximately, around, or nearly is not an indefinite expression.)
   
   

   	in her forties (not 40s, ’40s, or 40’s)
   	a hundredfold
   	a thousand and one excuses
   	twelvefold

   
   
7. Use figures for numbers through the thousands; for larger numbers use figures and million, billion, etc.
   
   

   The collection includes more than 4 million volumes.

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PHYSICAL QUANTITIES

1. In scientific or technical writing, use figures to express area, distance, length, volume, and other physical measurements.
   
   

   	3 miles
   	-7o C
   	1 cubic foot
   	6 acres
   	9-volt battery
   	2 ems

   
   
2. In nonscientific writing, treat expressions denoting physical quantities according to the general rule (spell out numbers under 10; use a figure for numbers of 10 or more). Always spell out zero.
   
   

   	The city got nine inches of snow within 12 hours.
   	Her daughter will soon be three years old.
   	The temperature dropped to 20 degrees below zero.

   
   
3. Use figures for fractional quantities that would be cumbersome written out.
   
   

   These should be typed on 81/2-by-11-inch bond.

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DATES

1. Use figures for dates.
   
   

   On December 22, 1869, William Watts Folwell was inaugurated as the first president of the University.

   
   
2. Do not use st, d, and th after dates to indicate ordinals.
   
   

   	Student elections are scheduled for May 26.
   	not
   	Student elections are scheduled for May 26th.

   
   
3. Spell out references to particular decades; do not capitalize them.
   
   

   roaring twenties (but the 1920s)

   
   
4. In informal contexts, the year may be abbreviated.
   
   

   	the class of ’53
   	the spirit of ’76

   
   
5. When using two years to show an inclusive period, use an en dash to separate the numbers; do not repeat the century.
   
   

   the 1979–81 biennium (not the 1979–1981 biennium)

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TIME OF DAY

1. In text, spell out time of day unless you are referring to a precise time.
   
   

   	Staff meetings never end before five.
   	His parents insisted that he be home by midnight on weekends.
   	but
   	The bus leaves Duluth at 6:45 each evening.
   	KTCA will air the show tomorrow morning at 8:30.

   
   
2. Always use figures with a.m. and p.m. Never use morning with a.m., or evening with p.m., and never use o’clock with a.m. or p.m.
   
   

   	8 a.m.	12 p.m. (noon)
   	4:30 in the morning	12 a.m. (midnight)
   	9:45 p.m.	6 o’clock

   
   
3. In text, do not use ciphers (zeros) with even hours, except for consistency within a series.
   
   

   	Minnesota will return to standard time at 2 a.m. Sunday.
   	Morning presentations were scheduled for 8:30, 10:00, and 11:30.

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1. Use figures for monetary amounts. Use cents with amounts of less than a dollar; use the dollar sign for amounts of a dollar or more.
   
   

   	Back then you could send a letter for 4 cents.
   	The fee amounts to about $1.50 per student.

   
   
2. Do not use ciphers (zeros) with even dollar amounts, except for consistency within a series.
   
   

   	Students pay only $1 per film.
   	She paid $27.50, $18.00, and $16.95 for the three texts.

   
   
3. For monetary amounts of more than a million dollars, use the dollar sign and spell out million, billion, etc. Never use a hyphen within such numbers.
   
   

   	$2 million
   	a $4.87 billion loan
   	$10 million to $12 million

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1. Use figures for decimals and percentages. In nonscientific copy, use the word percent; in scientific or statistical copy, use the symbol %.
   
   

   	Less than 2 percent of the annual budget goes toward student aid.
   	Total saturated fatty acids were 48% and 37% for the two carcasses.
   	According to the counseling staff, employment opportunities reached 1.8 jobs per student that year.

   
   
2. Use a zero before the decimal point, but omit zeros after the decimal point unless necessary to indicate exact measurement. An exception to this rule is grade point average, which should always include two decimal places.
   
   

   	0.364
   	1.5 (not 1.50)
   	2.00 GPA (not 2.0 GPA)

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1. Follow the usage of companies, organizations, etc., in their official names.
   
   

   	Big Ten
   	7-Eleven Stores
   	4 -H Club

   
   
2. Use spelled-out ordinals to designate a religious organization or house of worship.
   
   

   	First Church of Christ, Scientist
   	Seventh-day Adventist

   
   
3. Use spelled-out ordinals to designate particular governments and governing bodies that are part of a succession.
   
   

   	First Continental Congress
   	Third Reich
   	Ninety-third Congress

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1. Form plurals of spelled-out numbers following the rules for forming the plurals of other nouns. Form plurals of figures by adding s alone (without an apostrophe).
   
   

   	sixes
   	hundreds
   	Temperatures soared to the 80s and 90s.
   	Cooperative food stores became popular in the 1970s.

   
   
2. In any number containing four or more digits, use a comma between groups of three digits, counting from the right. Exceptions are: serial numbers, common and decimal fractions, astronomical and military time, radio call numbers of not more than four digits, page numbers, addresses, zip codes, and year numbers.
   
   

   	7,934
   	4,634,912
   	serial number 12718
   	1200 on your radio dial
   	.04721
   	Look on page 1021.

   
   
3. Do not repeat a spelled-out number in figures. Such usage is appropriate only in legal documents.
   
   

   	The course must be taken sequentially over three quarters.
   	not
   	The course must be taken sequentially over three (3) quarters.

   
   
4. Spell out any number of less than 100 that precedes a compound modifier containing a figure.
   
   

   	two 1/2-inch boards
   	114 12-inch rulers
   	twelve 14-foot poles
   	five three-room apartments

   
   
5. When using symbols with two or more quantities, repeat the symbol.
   
   

   	81/2" x 11"
   	$6–$9

   
   
6. Spell out fractions standing alone or followed by of a, of an, or of the.
   
   

   	One tenth was considered a fair amount.
   	Three fourths of an inch.

   
   
7. Use figures for fractions that function as unit modifiers.
   
   

   	1/2-inch brick
   	11/2-foot-long board

   
   
8. Always use figures with abbreviations or symbols.
   
   

   	6 lb.	9¢	2 hr.
   	3 in.	7 kg	4 mm

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Dates

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