Part of the answer to this depends on whether you are learning the American versus British English variant.
In British English, one would say
That cake had one hundred calories in it
That cake had one hundred calories in it
In American English, one would more typically say
That cake had a hundred calories in it
That cake had a hundred calories in it
Additionally there are other differences between how numbers are stated in British versus American English that often cause confusion for new learners:
This bicycle cost two thousand, one hundred thirty seven dollars
This bicycle cost two thousand, one hundred thirty seven dollars
Would be a valid American englishEnglish number -, i.e. $2137, whereas in British English one would preferentially use the form
This bicycle cost two thousand, one hundred **and** thirty seven pounds.
This bicycle cost two thousand, one hundred and thirty seven pounds.
Meaning the same number - £2137.
In both American and British English, you need to qualify the number with "a" or "one" when stating an exactitude, for example
This book has hundred pages
This book has hundred pages
Is wrong in both American and British English. However, you can use the plural form of the quantity without "a" or "one" for indefinite quantities to express an order of magnitude:
This book has hundreds of pages
This book has hundreds of pages
Which would be used either idiomatically to mean
This book has lots of pages
This book has lots of pages
Or precisely to mean that the book has somewhere between 100-999 pages.
Part of the answer to this depends on whether you are learning the American versus British English variant.
In British English, one would say
That cake had one hundred calories in it
In American English, one would more typically say
That cake had a hundred calories in it
Additionally there are other differences between how numbers are stated in British versus American English that often cause confusion for new learners:
This bicycle cost two thousand, one hundred thirty seven dollars
Would be a valid American english number - i.e. $2137, whereas in British English one would preferentially use the form
This bicycle cost two thousand, one hundred **and** thirty seven pounds.
Meaning the same number - £2137.
In both American and British English, you need to qualify the number with "a" or "one" when stating an exactitude, for example
This book has hundred pages
Is wrong in both American and British English. However, you can use the plural form of the quantity without "a" or "one" for indefinite quantities to express an order of magnitude:
This book has hundreds of pages
Which would be used either idiomatically to mean
This book has lots of pages
Or precisely to mean that the book has somewhere between 100-999 pages.
Part of the answer to this depends on whether you are learning the American versus British English variant.
In British English, one would say
That cake had one hundred calories in it
In American English, one would more typically say
That cake had a hundred calories in it
Additionally there are other differences between how numbers are stated in British versus American English that often cause confusion for new learners:
This bicycle cost two thousand, one hundred thirty seven dollars
Would be a valid American English number, i.e. $2137, whereas in British English one would preferentially use the form
This bicycle cost two thousand, one hundred and thirty seven pounds.
Meaning the same number - £2137.
In both American and British English, you need to qualify the number with "a" or "one" when stating an exactitude, for example
This book has hundred pages
Is wrong in both American and British English. However, you can use the plural form of the quantity without "a" or "one" for indefinite quantities to express an order of magnitude:
This book has hundreds of pages
Which would be used either idiomatically to mean
This book has lots of pages
Or precisely to mean that the book has somewhere between 100-999 pages.
