Fifteen or Ten? Mastering the Correct Writing and Reading of the Number 5 in Mathematics

Five

“Five” is a noun representing the pronunciation of the number 5 in specific contexts, used to count numbers following the tens place.

Example: fifteen, twenty-five, thirty-five, etc.

Year

“Year” is also a noun with various meanings depending on its usage.

• Time taken for Earth to complete one orbit around the Sun: 1 year = 365 days, 5 hours, 48 minutes, and 40 seconds.
• A period equivalent to 12 months: e.g., first-year student.

Fifteen or Ten? Which is Correct?

Essentially, both pronunciations are correct, but the right one depends on the context. Fifteen represents the number 15, while ten represents the number 10. To distinguish between these numbers when speaking, consider the following methods:

• Use ordinal numbers or unit words. For example, fifteen can be expressed as “the fifteenth” or “fifteen items,” while ten can be “the tenth” or “ten items.”
• Use time or distance indicators. For instance, fifteen can be “a minute and a half” or “one-fifteenth,” while ten can be “a minute” or “one-tenth.”

However, there are instances where “năm” is used to denote a number, as in the following examples:

• 9.5: Nine point five
• 105: One hundred and five
• 155: One hundred and fifty-five.

Writing “one hundred and fifty-five” as “một trăm năm mươi năm” could be misinterpreted as “150 years” or “150 years old.” This is why “lăm” is now commonly used to differentiate from “năm.”

This phenomenon stems from mispronouncing the initial consonants L and N in certain regions, which has become a widespread and standardized practice. Some areas even use “nhăm,” such as “mười nhăm” for 15 or “hăm nhăm” for 25. According to educational curricula, teachers typically instruct students to read and write “lăm” instead of “năm,” making it a universal practice in language usage.

Standard Writing and Reading of the Number 5 in Mathematics

When counting ordinal numbers, “năm” and “lăm” are used in different positions. The rules are as follows:

• Use “lăm” when the tens digit is between 1 and 9. For example, 15 is read as “fifteen,” 25 as “twenty-five,” and 35 as “thirty-five.”
• Use “năm” when the tens digit is 0 or when combined with the unit word “mươi.” For example, 105 is read as “one hundred and five,” and 2455 as “two thousand four hundred and fifty-five.”

Rules for Writing Fifteen or Ten

In the number sequence XXX:

• If the number is in the form 5XY: Write as “năm.”
• If the number is in the form X5Y: Write as “năm.”
• If the number is in the form XY5: Write as “lăm” if Y > 0, and “năm” if Y = 0.

Thus, “lăm” is used only for the units place, but if preceded by a zero, it is read as “linh năm” or “lẻ năm,” distinguishing it from “năm” in dates.

Examples:

• 50, 500, 550 – where 5 is not in the units place: fifty, five hundred, five hundred and fifty.
• 15, 25, 155 – where 5 is in the units place: fifteen, twenty-five, one hundred and fifty-five.
• 105, 1005 – where 5 is preceded by a zero: one hundred and five, one thousand and five.
• Additionally, numbers from 25 to 95 can also be read as: twenty-five, ninety-five. However, this is less common and not recommended.

Reading the Number 5 in Mathematics

After understanding the rules for reading fifteen or ten, apply them to the following examples:

• 5: Five
• 15: Fifteen
• 25: Twenty-five
• 50: Fifty
• 95: Ninety-five
• 105: One hundred and five
• 125: One hundred and twenty-five
• 150: One hundred and fifty
• 155: One hundred and fifty-five
• 555: Five hundred and fifty-five
• 1005: One thousand and five
• 1025: One thousand and twenty-five
• 1125: One thousand one hundred and twenty-five
• 1500: One thousand five hundred

Reading and writing the number 5 in Vietnamese depends on its position in the number sequence. The general rule is as follows:

Using “Lăm”

Use “lăm” when 5 is in the units place and preceded by a number greater than 0.

Examples: 15 (fifteen), 25 (twenty-five), 35 (thirty-five), 45 (forty-five).

Using “Năm”

• When 5 stands alone: “five.”
• When 5 is in the units place but followed by “mươi”: 50 (fifty).
• When 5 is in the hundreds or thousands place: 105 (one hundred and five), 205 (two hundred and five).

Specific Examples:

• 105: One hundred and five.
• 2455: Two thousand four hundred and fifty-five.
• 5555: Five thousand five hundred and fifty-five.
• 555555: Five hundred and fifty-five thousand five hundred and fifty-five.

Why the Confusion?

The confusion between fifteen and ten arises from various factors, most notably regional pronunciation differences. Some people habitually mispronounce “lăm” and “năm,” leading to incorrect usage in writing. Therefore, to avoid mistakes, it’s essential to understand the essence of each term and use them correctly in context.

Guidelines for Writing Common “Năm/Lăm” Pairs

Five Million or Five Million?

The correct writing is “five million.” Since “million” is a large unit, the number 5 before units like million or billion is written as “năm.”

Five Thousand or Five Thousand?

The correct writing is “five thousand.” Similarly, when 5 precedes “thousand,” it is written as “năm.”

Fifty Million or Fifty Million?

The correct writing is “fifty million.” When 5 precedes “mươi,” the correct writing is “fifty.”

Fifth or Fifth?

The correct writing is “fifth.” When indicating a day of the week or an ordinal number, always use “thứ năm.”

Fifty-Five or Fifty-Five?

Both writings are correct, depending on the context.

• “Fifty-five” is used to denote the number 55, e.g., “I have lived fifty-five years.”
• “Fifty-five” is used to indicate a period of 55 years, e.g., “I have worked here for fifty-five years.”

Five Hundred or Five Hundred?

The correct writing is “five hundred.” When 5 precedes “hundred,” the correct writing is “five hundred.”

Fifty-Five or Fifty Years?

• “Fifty-five” is used to denote the number 55, e.g., “He is fifty-five years old.”
• “Fifty years” indicates a period of 50 years, e.g., “I have lived here for fifty years.”

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