1. Yesterday was his 100th day.
2. one hundredth day
3. a hundredth day
(How can we read '100th day'?)
Do you mean his 100th birthday? (Meaning he's 100 years old?)
Let me know.
and you can't say #3
To read "100th day," you have a few options:
1. First, you can read it as "one hundredth day." This is the most straightforward reading, where you simply say the number "one hundredth" followed by the word "day."
2. Another option is to read it as "a hundredth day." In this case, you say the word "a" followed by "hundredth" and then "day." This is less common than using the words "one hundredth," but it still conveys the same meaning.
Overall, both readings are correct, and you can choose the one that feels more comfortable to you.