Mistake in a module 3.7 example?

In module 3.7, I think one of the examples may be wrong. The example is: Noi viaggiamo meno veloci in treno che in aero.
In this sentence, I think less fast  (meno veloci) is being used as an adverb to modify the verb, we travel (viaggiamo), by describing the speed of travel.  I don't think it is being used to modify the plural subject, we (noi).  As an adverb, veloce should not change gender or number, and so I think it should be veloce, not veloci.  Am I wrong in this analysis?  Is veloci being used as an adjective to modify noi, or is there some other reason is is in the plural veloci?

Hi Thomas,

The proper adverb here is velocemente, as in viaggiare velocemente.
Viaggiare veloce is also a common expression, although it's mostly used in the spoken language. In this case, however, you have an adjective intead of an adverb, so you need to change it according to the gender and the number of the subject.

Veloce is for both masculine and feminine singular subjects.
Veloci is for masculine and feminine plural subjects.

Noi is usually followed by a plural, masculine adjective. The only case you would use the feminine version is when talking about a group (you + the other people with you) consisting strictly of girls.

Of course, you could also say Noi viaggiamo meno velocemente in treno che in aereo!

Hope this helps, and sorry for being late,

Lucia