How to use "tens of" and "hundreds of"?
Solution 1:
In English, one would normally say "dozens of" rather than "tens of", so there is some overlap. I might use "dozens of" for an amount between 36 (a dozen, two dozen, dozens...) and 132 (a dozen less than a gross), "scores of" for a number between 40 and 199, and "hundreds of" for values greater than that. I don't think I've ever thought about the reasoning behind this; it would really depend on which number sounded better in the areas which overlap.
Solution 2:
As I understand it, the usage is:
Tens of -- rarely used; "as many as XX" might be more appropriate
Hundreds of -- any number from 100 - 999; "more than 500" might be more appropriate for numbers greater than 500
Thousands of -- any number from 1,000 to 9,999
Tens of Thousands of -- any number from 10,000 to 99,999
Hundreds of Thousands of -- any number from 100,000 to 999,999; after 250,000, it is more appropriate to use quarter, half and three-quarter million
Solution 3:
When describing victims of a disaster, "tens of" usually means less than a hundred or a bit more, and "hundreds of" can mean up to a thousand or a few more. "Hundreds of dead" could be over a thousand, but the results are still unsure.
"Hundreds of" and "thousands of" are more common than "tens of", but if I heard the statement, I would expect "tens of" to be 30 to about 120 or so. A more common phrase for the same general amount is "dozens of".
Solution 4:
I have only heard of "tens" used in, "tens of thousands." Otherwise "scores" is used. Scores being 20-199. And "hundreds" is plural so it would be 200-1999.