• Although usage varies, most people spell out numbers that can be expressed in one or two words and use figures for other numbers:
• over two pounds
• six million dollars
• after thirty-one years
• eighty-three people
• after 126 days
• only $31.50
• 6,381 bushels
• 4.78 litres  

Days and Years

• December 12, 1965 or 12 December 1965
• A.D. 1066
• in 1900
• in 1971-72 or in 1971-1972
• the eighties, the twentieth century
• the 1980’s or the 1980s

Time of Day

• 8:00 A.M. (or) a.m. (or) eight o’clock in the morning
• 4:30 P.M. (or) p.m. (or) half-past four in the afternoon

Addresses

• 16 Tenth Street
• 350 West 114 Street

Identification Numbers

• Room 8
• Channel 18
• Interstate 65
• Henry VIII

Page and Division of Books and Plays

• page 30
• chapter 6
• in act 3, scene 2 (or) in Act III, Scene ii

Decimals and Percentages

• a 2.7 average
• 13 1/4 per cent
• .037 metric ton

Large Round Numbers

• four billion dollars (or) $4 billion
• 16,500,000 (or) 16.5 million

Notes on Usage

Repeat numbers in legal or commercial writing.

• The bill will not exceed one hundred (100) dollars.

Numbers in series and statistics should be consistent.

• two apples, six oranges, and three bananas
• NOT: two apples, 6 oranges, and 3 bananas
• 115 feet by 90 feet (or) 115′ x 90′
• scores of 25-6 (or) scores of 25 to 6
• The vote was 9 in favour and 5 opposed

Write out numbers beginning sentences.

• Six per cent of the group failed.
• NOT: 6% of the group failed.

Use a combination of figures and words for numbers when such a combination will keep your writing clear.

• Unclear: The club celebrated the birthdays of 6 90-year-olds who were born in the city. (may cause the reader to read ‘690’ as one number.)

• Clearer: The club celebrated the birthdays of six 90-year-olds who were born in the city.

Numbers that represent time, dates, ages, sizes, scores, money, and points on a scale

• in about 6 years
• 2 days ago
• at 12 noon
• $5
• 6-year-old children

Numbers that represent a place in a series

• year 7 of an 8-year project
• room 9
• Figure 2 (in an article)
• Chapter 5
• row 1

Numbers in a list of four or more numbers

• 1, 2, 4, and 8 bits, respectively

Numbers less than 10 that do not represent exact measurements.

• only three times
• four 32-bit words
• eight lists
• nine pages
• a three-way interaction

Any number that begins a sentence, title, or heading.

• Sixteen-bit processors were used.
• Thirteen of 20 processors failed.

Common fractions

• one-fifth of the users
• execution time was reduced by two thirds
• in one half the time

Widely accepted phrases

• the Fourth of July
• the Ten Commandments

Combined figures and words.

• 3 million cycles
• 32 million bytes
• in 2 three-part modules
• twenty-four 8-bit words

Ordinal numbers.

Treat ordinal numbers as cardinal numbers

• a second-order relationship
• a third-generation chip
• the 3rd and 12th rows of the matrix

Exercise 1: Each sentence contains at least one error. Correct them.

1. I bought 3 computers.
2. I bought three computers and 20 printers.
3. 10 people came to the meeting at 10 o’clock.
4. They have sold four million copies of this software so far.
5. The 1st new computer system is ordered already.
6. I’ve tried this 2 or 3 times.
7. This sentence is 6 words long.
8. This increases processing speed by five per cent.
9. The screen is 32.56 cm wide and eight cm tall.
10. Look in lab number seven.
11. Chapter 7 of this book begins on page 1,230.
12. The probability of getting this relationship by chance is less than 0.05.
13. 2 or three weeks ago that bug was fixed.
14. They voted by a 2/3 majority.
15. When the result is multiplied by one hundred, you get a percentage.
16. The first and tenth lines of the matrix contain 0s
17. Two two-part modules were added.
18. All of these 8’s have to be written as words.
19. Please wait outside Room Seven.
20. This chip has a drawing speed of eight ns/pixel with 32 bits per pixel.