Either one is okay.
I’m from the US and I’m sure I sometimes use AND and sometimes don’t. I feel like it’s more correct to not say AND, though.
I’m from the U.S. and my math teacher taught me the same thing. I promptly ignored her after the test where we had to write out numbers and went back to speaking liking a normal person. “And” it is.
It’s one hundred five because the decimal point is read as “and”.
Example: 105.26 - One hundred five and twenty-six one hundredths.
If you used “and”, it would be - one hundred and five and twenty-six one hundredths
As we all know, “two ‘ands’ don’t make a right!” 
I don’t know why I have such a strong memory of this, but I distinctly remember being told by my 1st grade teacher (in my American 1st grade class) that we do not use “and” in such situations. I presume she corrected us until we got it right. I don’t have too many memories from 1st grade but weirdly, this is one.
I’m sure I say “and” all the time but I would definitely not write it. I of course would not be confused or put off by anyone saying it, or writing it in a casual setting, but I think in formal writing (say, a news article) I would definitely be put off by someone using it.
This, but also this:
This is the way I would write it on a check, which is the only place I can think of that I would actually write out the words.
When speaking, I, like MrAtoz, would say the decimal point as “point.” The exception is money: I might say $105.26 as “One hundred five dollars and twenty-six cents.” Saying "“One hundred and five dollars and twenty-six cents,” sounds less good, though not out-and-out wrong, to me.
One Oh Five
Depends on context. Informally, it’s “A hundred and five”. Written in the long verbose part of an old-fashioned paper check, it’s “One Hundred Five Dollars” (but if there are cents, “One Hundred Five Dollars AND 12/100”). If I’m reading off numbers, it’s likely to be “One Oh five” or “One Hundred Five”.
Not American, use both, as well as ‘one oh five’, ‘a buck five’, or ‘one five’, depending on circumstances (euphony, clarity, speed, mood).
I was also taught that the addition of an “AND” when writing out a number properly indicated the addition of a fraction, but the only place this typically comes up is when writing a check.
To wit, if I am writing out a check for $105.33, I write out “One hundred - five AND 33/100 dollars.”
Because of this, I would typically pronounce 105 the same way: “one hundred-five.” (However, I might also say “one oh five.”)
Yeah, I don’t say one hundred five or one hundred and five. I’d nearly always say one oh five.
If you forced me to say one, I guess I’d say “one hundred and five” because “one hundred five” is so alien I’d have to think about what amount it even was trying to convey.
I’m from the USA and use both, but when I was a kid I was taught that adding “and” is grammatically incorrect. Until reading this thread I don’t think I’ve ever run into anyone that was confused by either use.
Question: How would you pronounce the number 105,000? “One hundred five thousand” or “one hundred and five thousand”? And is this different from how you’d pronounce 105?
uh hunderd n five touse n
“hunnert’n’five”
I hate it when people are so lazy they don’t put an ‘uh’ in front of that.
This. I was I elementary school from 1960 to 1966.
Strictly speaking the “and” should not be used and I don’t use it if I’m writing numbers, but just about everybody uses it when they talk, including me. (U.S.)
I hate this “and” rule. As a third grade teacher, I’m supposed to be the gatekeeper for it and fingerwag at kids, but I refuse to do so. Instead I teach my students that the “rule” exists, but it’s a convention, not a mathematical thing, and most people ignore it in speaking, and that very rarely they’ll find someone who will judge them for saying the “and,” so they should at least know about the rule.
But for students who struggle with math, the “and” is often very useful for understanding place value. I can show them that if you’re adding 500 and 47, you get “five hundred and forty seven.” They can see how the numbers add together. A small thing, but those kids need every small thing they can get.
When using a decimal I do not say “one hundred and five decimal 5” but “one hundred point five”. 105 would be “one hundred and five”.