Diana, There really is no rule that applies 100% of the time. Certain ways are a little more common and certain ways are a little less common, but any of them can be easily understood. In most modern English writing, these numbers probably wouldn't be spelled at all. Instead, they would be written using digits, like this "103" or "1103" or "1,103." We usually only write out the numbers between one and nine or maybe ten. Most of the time, higher numbers than ten use digits. But again... there aren't really "absolute" rules. These numbers are commonly spoken many different ways: 103: "one hundred three" "one hundred and three" "hundred three" "a hundred three" "a hundred and three." 1103: "eleven oh three" "eleven hundred three" "eleven hundred and three" "a thousand, one hundred and three" "one thousand, one hundred three" "one thousand, one hundred and three" If for some reason you had to write them out the most common way is this 103: "one hundred and three" 1103: "one thousand, one hundred and three"

Correct. 103 is spelt, one hundred and three. The number 100, and 3. 1103 is spelt, one thousand one hundred and 3. You wouldn't say, one thousand and one hundred and 3. You only say and before the last digit.

My job in the US involved a lot of business writing. I'm not familiar any rule that requires spelling numbers >100 number with or without "and" before the last number. Except when writing a check, the convention is to only spell numbers 0-9, and to use numbers for higher numbers.