# Numbers in Writing: 10 Simple Rules (Part 2)

Continuing from the last post, here is the second post in our series of simple rules on number conventions in formal writing.

## Rule #6

Spell out numbers that express the time, but use numerals if you use AM and PM times based on the twenty-four hour clock can be expressed in numerals.

Example

Avoid: The lay panel retired at five pm the previous evening and worked until five am the next day.

Use: The lay panel retired at 5 pm the previous evening and worked until 5 am the next day.

Alternatively use: The lay panel retired at 17:00 the previous evening and worked until 05:00 the next day.

## Rule #7

Spell out amounts of money that do not involve change, and write out the unit of currency as well. If you use symbols for currency, write the amount in numerals. Also use numerals to express exact amounts of money.

Example 1

Avoid: Also, twenty-seven dollars cannot be exchanged into 22 dollars and then re-invested.

Use: Also, twenty-seven dollars cannot be exchanged into twenty-two dollars and then re-invested.

Alternatively use: Also, \$27 cannot be exchanged into \$22 and then re-invested.

Example 2

Avoid: His total travel cost was thirteen pounds sixty-five pence.

Use: His total travel cost was £13.65.

## Rule #8

Use numerals when writing dates. Days nine and below that precede the month, or appear alone can be written out.

Example

Avoid: The operation was scheduled for January fourth.

Use: The operation was scheduled for January 4th.

Alternatively use: The operation was scheduled for the fourth of January.

## Rule #9

Use numerals for percentages. In technical contexts, the symbol % should be used.

Example

Avoid: Their study shows that thirty-five percent of American parents play videogames.

Use: Their study shows that 35 percent of American parents play videogames.

## Rule #10

When writing a list that includes numbers, be consistent, rather than follow individual rules.

Example

Avoid: In the surviving-negative group, five out of 20 patients were alive in first CR.

Use: In the surviving-negative group, 5 out of 20 patients were alive in first CR.

In our next issue, we will deal with more specific styles relevant to biomedical writers.

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