Translation:A conman and three murderers are in jail.
They haven't taught this numerical case here in Duolingo, so they don't want to confuse Russian learners.
By the way, the words двое, трое, четверо, пятеро etc. are the only choice when, talking about a group of humans which includes at least one male person, you translate phrases like "these three" or "the other two" into Russian. Examples: Эти трое ничего не знают. Оставшиеся двое займутся приготовлением обеда.
We also use collective numerals when we don't know if a male person is present in the group or not.
Killer is also "убийца" (should be accepted) Rascal is "мошенник" (should be accepted) Actually, lots of words should fit "мошенник"
swindler, embezzler, crook, charlatan, mountebank, gyp, fraud, sharper, cheat, faker, deceiver, rip-off artist, chiseler, and, of course, confidence man (because con man is simply shortened from it).
"Gyp" is a derogatory term for Gypsies/Roma people, like "Jap" for Japanese. Bad choice!
But don't forget "flim-flam man" and "hornswoggler"!
I don't think being a rascal is a crime, though, so... that would be a little silly.
Rascal is more about a sly person or a villain but not about a criminal in terms of the law. And there is difference between killer and murderer. Killer is more wide in meaning. To kill is not only about people, for example dog killer, killer shark, killer flood, but murderer is only about people who kill people without justification or excuse. For example a soldier at war is also killer but not murderer. And crime is called a murder in the court. Of cause a murderer can be named killer, especially if he is a serial killer or slayer if he is a violent one.
When убийца refers to a human, it always means "murderer" even if the word "killer" is used (e.g. a serial killer).
Here сидят means "are doing/serving term". The word could have been omitted but wasn't, so there is no reason to omit the phrase into which it translates in the English sentence.
In Russian, if someone asks, "Где он?" and gets "Сидит" as an answer, it will be understood that the guy in question is behind bars.
The conman and three murderers are imprisoned.
The last word did not accepted.
What is wrong?
It should be accepted; it's close enough. The verb imprisoned is usually used in the present perfect tense, though. "The conman and three killers have been imprisoned."
почему "три убийцы" а не "три убийца"? I thought that after nubers one, two, three and four the родительный case of the singular number is used
Of cause you're correct that genetive case of убийца is убийцы but not in that case. In genetive it would be like 'нож убийцы' - 'the killer's knife' but here we have plural nominative 'three killers' - 'три убийцы'
No, три убийцы, "убийцы" is not plural nominative. It's singular genitive. Think of it as "three of a killer."
Нахватался из других языков. У тех же чехов после числительных идет plural nominative
Yes, you're right in this moment. Almost forgot this moment after school time )))
Just to clarify an additional detail from the question - Only 2, 3 and 4 take genitive singular. "1" does not. It would still be один человек, одна женщина, одно окно.
That's interesting. In Slovak, it's troch vrahov, the plural genitive. In Russian, враг (vrag) means "enemy."
враг is enemy but in czech vrah is a killer or murderer and enemy is nepřítel or in russian неприятель. And as far as I remember in Czech they use nominative plural for 2-4 and for 5 is genetive plural - pět vrahů. I thought the same in Russian because i have already forgotten school grammar lessons )))
I guess убийцы is an irregular word, in which both plural nominative and singular genitive are the same. With the word враг, plural nominative is враги, 2-4 plural uses the singular genitive врага, and 5 or more plural uses the plural genitive врагов.
I believe we can find something in one of the Rosenthal's guidebooks but I'm too lazy for that :-)
I don't think it is irregular at all - that's standard for most words ending in -a (though in some cases the stress shifts).
There is hardly anything irregular here. Pretty much all nouns that share the declension of мама or кошка share this feature, unless they have a different stress in one of these forms (e.g., сестры/сётры or земли́/зе́мли)