How should you read the number 1.5?
Should I read it as
- one and half
- one and a half
Any help would be appreciated.
You have several options:
These are all correct.
The hyphens in the last two are optional to some degree depending on the source. Including it is arguably more correct.
one and half is not correct... usually. Based on your comments, it looks like you're seeing it used in technical, electrical system uses:
In this case, it may be correct but I don't see any evidence that they would ever write it out as 1.5.
"1.5" would be read as "one point five". Note that "1.50" is "one point five oh" or "one point five zero", not "one point fifty", since fifty means five times ten.