Darf ich mit eurem Fahrrad fahren?

Would “Kann ich eurem Fahrrad fahren” be correct or at least understandable.  There are two things I am wondering about in this sentence.  1. Why Darf vs Kann, and 2., how do you know when to insert the “mit” into a dative phrase?

Hallo JosephP50, 

Both “Kann ich mit eurem Fahrrad fahren?” and “Darf ich mit eurem Fahrrad fahren?” would be correct. “Darf ich mit eurem Fahrrad fahren?” is perhaps a wee bit politer. You can think of it as “May I ride your bike?”

In German, a lot of verbs are paired with specific prepositions (e.g. “mit”, “auf”, “an”). These form so-called prepositional objects which require a specific case. In this case, the verb fahren is paired with the preposition mit and requires the dative case. 

You can simplify the sentence into: "Ich fahre mit eurem Fahrrad." - “I ride your bike.”

You can ask for the object using the proposition, e.g.: “Womit fahre ich?” - “What do I ride (with)?” Answer: “mit eurem Fahrrad” - “with your bike”

You can think of it as talking about a specific object, “your bike”, in this case. A more general question, that doesn't require a preposition, would be: “Kann ich Fahrrad fahren?” - “Can I ride (a) bike?”

Hope this helps!

Julia

Thank you.  Of course the lessons have to show one answer, and in this case they chose Darf rather than Kann, and I get that.  But as a sudent trying to figure out whether it is a preference or if it is the only correct answer, it is difficult--thus the question.