Pronunciation of conjugated verbs
I'm a little confused when the ending of a verb is pronounced and when it is not. For example "manger" - mangeons ( the -ons is pronounced) but mangent (the - ent isn't).
Firstly, am I correct and secondly is there a rule?
First, you are correct. Manges, mange and mangent all sound the same, Mangeons and mangez are the exceptions. There was a different pronunciation question asked earlier. Although it is not the same the answers may be useful : http://duolingo.com/#/comment/11828
I can't answer your second question. I don't know if there is a rule that covers everything, but the same pattern is found in all the verbs which are conjugated like "manger" - which is the most common type of verb. They say that all the new verbs recently arrived, or just arriving, in dictionaries are conjugated like this.
There is a very simple rule!
These conjugations are stem accentuated: 1. sg., 2. sg., 3. sg. and 3. pl.
These conjugations are ending accentuated: 1. pl., 2. pl.
(No idea if these words exist! In German you would call them "stammbetont" and "endungsbetont", sorry.)