How to write out numbers in compliance with British usage?

This question regards the numbers from 1 to 999. We can ignore commas, hyphens, and spaces. What I'm interested in is when and where to use the word "and".

There are a few interesting cases:

1) 20 < n < 100

Is it "twenty and one", or "twenty one"?

2) 100 < n < 120

Is it "one hundred and eleven"? "One hundred and one"? Or is it "one hundred one", "one hundred eleven"?

3) n = 190 (for example)

Is it "one hundred and ninety"? Or "one hundred ninety"?

4) n = 191 (for example)

I'm assuming it's "one hundred and ninety one"... Or is it "one hundred ninety and one"?

Thanks so much... I'd be very grateful if someone could answer these 4 cases :-)

Solution 1:

• 21: twenty-one
• 111: a hundred and eleven (or "one" hundred and eleven)
• 101: a hundred and one
• 190: a hundred and ninety
• 191: a hundred and ninety-one
• 206: two hundred and six
• 1,002: a thousand and two
• 15,726: fifteen thousand, seven hundred and twenty-six
• 276,521: two hundred and seventy-six thousand, five hundred and twenty-one
• 1,000,001: a million and one

All the numbers over a hundred have "and" in them where some other units are added after the "hundred". In fact, US English "a hundred one" strikes me as grammatically incorrect, as I can't agree that US English is just as correct as British English.