あの老人に何度注意したことか。

[kachibi]

I checked the Jisho Dictionary, it says 何度 means "how many times", while 何度もmeans "repeatedly many times".

But my Japanese language book gives a translation of this sentence as follow:

あの老人に何度注意したことか。
I have reminded the old man many times!

But the above sentence doesn't use 何度も, does that mean 何度（without も）can also mean "many times"?

 

[Flaminius]

The fuller version of this construction is: 何度注意したことかわからない。 This of course means, "I don't know how many times I scolded the old man." The "many times" sense arises from the whole construction, and it has become attached to the shorter version, too.

 

[gengo]

あの老人に何度注意したことか。

The 何度 here follows the same pattern as other 何- words, such as 何回 (how many times), 何人 (how many people), 何年 (how many years), and so forth. These 何- words are also similar in that when followed by も, their meaning changes from "how many" to "several/many."

But the above sentence doesn't use 何度も, does that mean 何度（without も）can also mean "many times"?

Not "many times," but "how many times." The か at the end is important because it tells us that the speaker is rhetorically questioning how many times he has warned the old man, as Flaminius says above.

 

[kachibi]

Thank you!

要するに、何度 still means "how many times" while "何度も” means "several times". But just the か of ことか makes 何度 in my sentence also have the "several times" sense, 正しですか？

 

[gengo]

要するに、何度 still means "how many times" while "何度も” means "several times". But just the か of ことか makes 何度 in my sentence also have the "several times" sense, 正しいですか？

あの老人に何度注意したこと is an incomplete sentence, and leaves the reader thinking "What...?" The か tells us that the speaker is wondering to himself. Without a も, I don't see any way that 何度 could be interpreted as "several times." The か does not do that.

 

[SoLaTiDoberman]

あの老人に何度注意したことか。
＝How many times did I warn that old man?

か is basically a question-making particle.
However, in this context, it is a rhetorical question, meaning that the speaker is asking or wondering to himself.
And it conveys the speaker's strong emotion such as "surpise," "anger," or "dissapointment."

How many times did I warn that old man？
＝I wonder how many times I warned that old man (but in vain.)

And in this context, "how many times" is also used as a rhetoric, meaning "so many times" or "such many times."
You can't reach the correct answer by analysing the grammatical syntax or structure.
You should think about the context, usage, and rhetoric.

How many times did I warn that old man？
＝I wonder how many times I warned that old man (but in vain.)
＝I wonder I warned that old man so many times, but in vain!

cf)
How many times do you make the same kinds of careless mistakes?
何回同じケアレスミスを繰り返せば気が済むんだ？
=Don't make the same kinds of careless mistakes. You've made them quite a lot already.

Is it clear?