"Many Finns speak English."
Translation:Moni suomalainen puhuu englantia.
Why not Monta Suomalaista Monia Suomalaista Or monet suomalaiset puhuvat??
I would use monet suomalaiset puhuvat englantia too, but the suggested translation doesn't sound too bad either. In fact, also the dictionary considers the two forms as equals, i.e. moni suomalainen puhuu is the same as monet suomalaiset puhuvat. Which one to use is a matter of taste. There's a problem if both of them aren't accepted.
According to Finnish grammar rules, certain cases are needed with certain words and contexts. Moni suomalainen is an idiomatical expression roughly equivalent to "many a Finn" and although it does not look like it, it does mean several people.
Monta requires you to have a certain case (partitive): monta suomalaista, monta appelsiinia, monta autoa – not
monta suomalaiset, monta appelsiinit, monta autot.
Or vice versa, if you want to use suomalaiset then you need to use monet: monet suomalaiset, monet appelsiinit, monet autot.
And, using moni: moni suomalainen, moni appelsiini, moni auto.
Well, no. Moni is a nominative form and it also requires that the following word is in nominative, the basic form, that is. Therefore you would need to use suomalainen in your case.
The structure also requires you to observe singular and plural. You could start building the sentence with either moni or monet, but if you started with moni, then it would be singular and need puhuu. Or vice versa, starting with monet would require the verb be puhuvat.
Singular: moni suomalainen puhuu (kind of "many a Finn speak(s)")
Plural: monet suomalaiset puhuvat ("many Finns speak")
The funny thing is that roughly they mean the same thing, despite having different plurality.
Edit: to add, the site Uusi kielemme has a good explanation on moni, monta, monet and how they are used.
This exercise is tricky because the example answer is singular while the English sentence is plural. This is because there is a quirk in Finnish language that makes certain constructs of different plurality equal (by meaning), and it's easy to mix up the words of different cases and pluralities.
Moni, even though meaning "many" things at once, is singular, whereas monet is the plural, and both cases need correct word forms (inflection). In another post it was explained that these two mean the same thing:
Singular: moni suomalainen puhuu (kind of "many a Finn speak(s)") Plural: monet suomalaiset puhuvat ("many Finns speak")
If you want, you can stick with the plural translation, that's all good, but beware of mixing words from different constructs. If you are interested, see also moni, monta, monet from the site Uusi kielemme.