Page 396 - Practical English Usage 3ed - Michael Swan, Oxford

In measurements containing two different units, and is possible before the smaller, but is usually left out.
two hours (and) ten minutes
two metres (and) thirty centimetres
In writing we generally use commas (,) to divide large numbers into groups of three figures, by separating off the thousands and the millions. Full stops (.) are not used in this way.
3,127 (NOT 3.127) 5,466,243
We do not always use commas in four-figure numbers, and they are not used in dates.
4,126 OR 4126 the year 1648 Spaces are also possible.
There are 1 000 millimetres in a metre.
Note the hyphen between the tens and units in twenty-one, twenty-two, thirty-six, forty-nine etc.
11 a and one
We can sayan eighth or one eighth, a hundred or one hundred, a thousand or one thousand, a million or one million, etc. One is more formal.
I want to live for a hundred years. (NOT • • . fa, hftntlreti years)
Pay M r J Baron one thousand pounds. (on a cheque)
A can only be used at the beginning of a number. Compare:
alone hundred
three thousand one hundred (NOT three th6f:t"tmti a hft,ttireti)
A thousand can be used alone, and before and, but not usually before a
number of hundreds. Compare:
alone thousand alone thousand and forty-nine one thousand, six hundred and two
(More natural than a thousand, six hundred and two.)
We can use a or one with measurement words. The rules are similar.
alone kilometre (B U T one kilometre, six hundred metres)
an/one hour and seventeen minutes (BUT one hour, seventeen minutes) alone pound (B U T one pound twenty-five)
12 numbers with determiners
Numbers can be used after determiners. Before determiners, a structure with ofis necessary.
You're my one hope.
One ofmy friends gave me this. (NOT One myfrientl . ..)
13 eleven hundred etc
In an informal style we often use eleven hundred, twelve hundred etc instead of one thousand one hundred etc. This is most common with round numbers between 1,100 and 1,900.
We only got fifteen hundred pounds for the car.
This form is used in historical dates (see 152).
He was born in thirteen hundred.
It was built in fifteen (hundred and) twenty-nine.
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