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2 added a necessary space, and few extra examples
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'Hundred' is the order of magnitude, just as 'twenty'shows the order of magnitude.

In the UK 'a hundred, a hundred and one, a hundred and two' etc is a common style when speaking about 100, 101, 102 etc. This form is also used when writing what has been spoken. 'One hundred' is also used. Either form is also used for 1,000, i.e.'a thousand', or 'one thousand'etcthousand' etc.

In the US, the form 'hundred' and 'thousand' is used with without the indefinite article 'a'. And 'one' is similarly not used when speaking about 100, or101, 102, 1000, 1001 etc.

'Hundred' is the order of magnitude, just as 'twenty'shows the order of magnitude.

In the UK 'a hundred, a hundred and one, a hundred and two' etc is a common style when speaking about 100. This form is also used when writing what has been spoken. 'One hundred' is also used. Either form is also used for 1,000, i.e.'a thousand', or 'one thousand'etc.

In the US, the form 'hundred' and 'thousand' is used with without the indefinite article 'a'. And 'one' is similarly not used when speaking about 100, or 1000 etc.

'Hundred' is the order of magnitude, just as 'twenty'shows the order of magnitude.

In the UK 'a hundred, a hundred and one, a hundred and two' etc is a common style when speaking about 100, 101, 102 etc. This form is also used when writing what has been spoken. 'One hundred' is also used. Either form is also used for 1,000, i.e.'a thousand', or 'one thousand' etc.

In the US, the form 'hundred' and 'thousand' is used with without the indefinite article 'a'. And 'one' is similarly not used when speaking about 100, 101, 102, 1000, 1001 etc.

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source | link

'Hundred' is the order of magnitude, just as 'twenty'shows the order of magnitude.

In the UK 'a hundred, a hundred and one, a hundred and two' etc is a common style when speaking about 100. This form is also used when writing what has been spoken. 'One hundred' is also used. Either form is also used for 1,000, i.e.'a thousand', or 'one thousand'etc.

In the US, the form 'hundred' and 'thousand' is used with without the indefinite article 'a'. And 'one' is similarly not used when speaking about 100, or 1000 etc.