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I am confused about using "of" with numbers. When do numbers come before or after the "of"?

After the "of"

A bill of £42.50

A height of 10 metres

A weight of 225 kilograms

Before the "of"

2 kilograms of apples

Millions of insects

12-mile stretch of fine sand

So, I wonder which of the following examples are true ?

1- 5 inch screen

2- 5 inch of screen

3- A screen of 5 inch

1'- 2 kilograms dumbbell

2'- 2 kilograms of dumbbell

3'- A dumbbell of 2 kilograms

2 Answers 2

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Some of your examples are valid but they would be used in different contexts. Also, some need to be plural and others singular.

Television and computer screens are measured diagonally. A 5 inch screen would measure 5 inches from the bottom left corner to the top right corner.

When we use a number ahead of a measure, we keep the measure singular. For example, a 10-kilometre run, a 20-pound weight, a 5-litre can.

Another way to say a 5-inch screen would be a screen of 5 inches. In this case it has to be plural - not 5 inch.

Someone who needed to mend a hole in a mosquito screen might require five inches of screen to cover the hole. To be precise, that would be either 5 square inches or, more likely, 5 inches square. Again, note the plural inches.

A dumbbell weighing 2kg is a 2 kilogram dumbbell. (Kilogram used in the singular here is a noun adjunct, acting as an adjective, like the examples above.)

If you were delivering a dumbbell in parts to somebody's door, you might say I have 2 kilograms of dumbbell for you - although this is an unusual way of putting it.

And a 2kg dumbbell can be described as a dumbbell of 2 kilograms although most people would simply call it a 2 kilogram dumbbell.

It's a matter of context.

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  • Thanks, one more question : Should I say "2-kilogram dumbbell" or "2 kilogram dumbbell" ? Are both okay ? Mar 5, 2019 at 16:23
  • "When we use a number ahead of a measure, we keep the measure singular. For example, a 10-kilometre run, a 20-pound weight, a 5-litre can." Can we use this rule with plural nouns ? For example : "500-page books" or "5-litre cans" Mar 5, 2019 at 17:11
  • Yes, the same rule applies to plural nouns - 200 kilogram lions. Measures are generally abbreviated after numbers. (abbreviations.yourdictionary.com/articles/…). When using the measure fully written, I should not use a hyphen, just a space. Where abbreviations are concerned, I have seen variations such as 20km, 20-km and 20 km. This may be a matter of style rather than of any rule. Others may be able to give you better guidance here. Mar 5, 2019 at 18:02
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With countable nouns in the plural and with uncountable nouns, we use:

  • X measure (in the plural) of Y

e.g. 2 kilograms of apples / 2 liters of water

With countable nouns in the singular, we can use:

  • (a) X-measure (in the singular) Y

or

  • (a) Y of X measure (in the plural)

e.g. a five-inch screen / a screen of five inches

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  • If I want to convert "books over 500 pages" to this form which one would be correct ? "500 pages of books"(that sounds wrong to me) or "500-page books" Mar 5, 2019 at 17:05
  • You can say "books of (over) 500 pages" or "500-page books".
    – Gustavson
    Mar 5, 2019 at 19:58
  • Thanks :) lastly I am allowed to use this form "2-kilogram apples" Mar 5, 2019 at 20:41
  • No. Pay attention to the letters X and Y I used. X stands for a number, and Y for the thing being measured. You should say "2 kilograms of apples". "2-kilogram apples" would mean "apples each weighing 2 Kg"!
    – Gustavson
    Mar 5, 2019 at 20:46

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