In a sentence like "The answer is 0.8." the period looks awkward after "0.8". Is there a rule for a situation like this? Sometimes I put a space before the period like this: "The answer is 0.8 ." However, that looks awkward too.
Either rewrite the sentence or paragraph so it doesn't end with the number, or write it as you should with any normal sentence and put a period at the end:
The answer is 0.8.
That looks much neater to me than
The answer is 0.8 ..
If you're not dealing with mathematics or plain numbers, then another approach is to mention the units (which is often a good idea anyway):
The answer is 0.8 litres.
It doesn't look strange to me, and it's not wrong.
Certainly, you don't want to
1. put a space after it, or
2. add a "spurious" phrase because that will (a) make the sentence illogical and (b) produce sloppy writing due to the unnecessary words.
The other advice you received is good:
1. Revise the sentence to avoid this issue,
2. Add the identifier, if possible (0.8 what?),
3. Get accustomed to it.
When we use a number without a decimal point at the end of a sentence, we use a period in a way we use it after the last word. The same rule should be applied for ending the sentence whether it ends with a word or a number, with or without a decimal. If you refer to some accounting books, they use it the same way you have used in your example.
Enter the total Taxable Amount of 400.00 and Total Tax Due City or Co. of $11.00.
I will write it as: The answer is 0·8. I have used an interpunct (
·) as the decimal point.
I get this situation sometimes in business emails. Most of the time I'll just put in an extra space and start the next sentence with capital letter:
i.e. "Please note that we have processed wire transfer payment for $25,250.75 Please confirm receipt when possible."
....or I'll just chill and have my latte. Don't sweat it.